Aus dem Institut für Tierzucht und Vererbungsforschung

Aus dem Institut für Tierzucht und Vererbungsforschung

der Tierärztlichen Hochschule Hannover

Evaluation of small group systems with elevated perches, furnished cages

and an aviary system for laying hens with respect to bone strength, keel

bone status, stress perception and egg quality parameters

INAUGURAL-DISSERTATION

zur Erlangung des Grades einer

DOKTORIN DER VETERINÄRMEDIZIN

(Dr. med. vet.)

durch die Tierärztliche Hochschule Hannover

Vorgelegt von

Britta Scholz aus Arnsberg

Hannover 2007

Scientific supervisor: Univ.-Prof. Dr. Dr. habil. O. Distl

1. Examiner: Univ.-Prof. Dr. Dr. habil. O. Distl

2. Co-examiner: PD Dr. Dr. habil. H. Salisch

Oral examination: 26.11.2007

To my family

Parts of this work have been submitted, are in review or have been accepted for publication in

the following journals:

Archiv für Tierzucht

Archiv für Geflügelkunde

Berliner Münchener Tierärztliche Wochenschrift

Züchtungskunde

Table of contents

Chapter I

Introduction ................................................................................................................................ 1

Chapter II

Evaluation of bone strength, keel bone deformity and egg quality of laying hens housed in

small group housing systems and furnished cages in comparison to an aviary system. ............ 5

Chapter III

Bone strength, keel bone deformities and egg quality of Lohmann Silver layers kept in small

group systems with modified perch positions in direct comparison to an aviary housing

system and furnished cages. ..................................................................................................... 19

Chapter IV

Bone strength and keel bone status of two layer strains kept in furnished small group systems

with different perch configurations and group sizes. ............................................................... 47

Chapter V

Effect of housing system, group size and perch position on H/L-ratio in laying hens. ........... 65

Chapter VI

Keel bone condition in laying hens: a histological evaluation of macroscopically assessed keel

bones......................................................................................................................................... 81

Chapter VII

Meta-analysis of welfare, egg quality, production and selected behavioural traits to evaluate

small group housing systems for laying hens........................................................................... 97

Chapter VIII

Summary ................................................................................................................................ 117

Chapter IX

Erweiterte Zusammenfassung ................................................................................................ 121

Appendix ................................................................................................................................ 131

Acknowledgements

List of abbreviations

AP Aviplus

b linear regression coefficent

BE back perch elevated

BFD bone fragment dislocation

BW body weight

CB cortical bone

CI confidence interval

cm centimetre

comp compartment

et al. et alteri

EU European Union

EV Eurovent

FC furnished cages

FCM fracture callus material

FE front perch elevated

g gram

GR group size

H/L-ratio heterophil/lymphocyte ratio

LB Lohmann Brown

LL layer line

LIN layer line

LS Lohmann Silver

LSL Lohmann Selected Leghorn

LSM least square means

LSMlog logarithmised least square means

LT Lohmann Tradition

max maximum

min minimum

MJ mega Joule

mm millimetre

MON laying month

n number

N Newton

NE non-elevated

NS not significant

p error probability

PE periostal ectostosis

PP perch position

Q1/Q3 25%/75%-quantiles

SAS Statistical Analysis System

SD standard deviation

SE standard error

SG small group system

ST stepped position of perches

SYS housing system

x mean

x~ median

Chapter I

Introduction

Chapter I: Introduction

Introduction Laying hen husbandry has always been a focal point in the discussion on ensuring animal

welfare and protection on the one hand and considering economic aspects, such as

competitive market capability in the laying hen industry on the other hand. Comprising the

period from 1995 to 2004, changes in German laying hen husbandry have clearly occurred

towards housing systems that are more appropriate to hens. Whereas in 1995 a proportion of

93.7 % of hens were kept in conventional cages, followed by floor keeping (4.6 %) and free

range husbandry systems (1.6 %), the percentage of keeping hens in conventional cages was

reduced to 77.4 % in 2004 and floor keeping and free range husbandry nearly equalled out to

11.7 % and 10.9 % respectively (STATISTISCHES BUNDESAMT, 2005). These changes

are primarily due to continuous, legal alterations on laying hen husbandry systems.

Conventional cages, offering hens 550 cm² space per layer and providing poor environmental

conditions due to limited floor space and lack of cage enrichments, have always been heavily

criticised. Inactivity osteoporosis in hens and resulting bone fractures is one of the major

welfare problems attributed to these types of housing systems. Increased criticism of animal

welfare activists and the consumer of egg products on keeping hens in conventional cages has

finally led to the EU Council directive 1999/74/EC, which was passed on July 19th, 1999.

The directive sets out minimum standards for the protection of laying hens within member

countries of the EU and brings about major changes in laying hen husbandry, particularly

from 2012.

In the EU, conventional cages will have to be completely phased out by the end of December

2011 and replaced by furnished cages, small group housing systems or alternative housing

systems. In contrast to conventional cages, furnished cages provide an enlarged floor space

(750 cm²/hen) and are enriched with perches, nest boxes, dust baths and devices to shorten

claws. The provision of cage enrichment, particularly perches, is supposed to enhance layers’

bone strengths by offering increased stimulus to move and jump. Small group housing

systems are further advancements of furnished cages. They are designed to keep group sizes

of up to 60 layers per compartment, thus offering hens a larger general floor space area and

therefore increased possibilities to move within their individual compartments.

The implementation of the EU directive 1999/74/EC into national law has confronted the

German laying hen industry with legal requirements far beyond the demands of the EU

directive. In Germany, conventional cages will have to be entirely banned by the end of 2008

already and furthermore, furnished cages will only be accepted until the end of 2020. Only

recently, the German legislation has approved the so called small aviary housing system as an

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adequate replacement for the use of furnished cages. So far, data on keeping hens in small

aviary housing systems is lacking and at the same time mandatory for a successful

implementation of these systems in the future. One of the major advancements of the small

aviary housing system compared to the small group system is the incorporation of perches at

two different heights within individual compartments. In addition, small aviary systems are

supposed to offer an enlarged floor space per hen (800 cm²) and enhanced compartment

heights (60 cm). These modifications aim at offering hens more opportunities to perform

natural behavioural traits and thus trying to combine increased animal welfare and high

hygienic standards, which are related to husbandry systems that are well protected from

outside environmental influences.

Alternative housing systems, such as aviary systems, are designed to keep very large groups

of layers in littered compartments and provide optional outdoor access. Aviary systems

demand more labour-intensive management skills and in addition, layers are permanently

faced with increased risk of infection due to contact with excrements and outdoor

environmental impacts. The occurrence of bird flu in a variety of European and non-European

countries in 2006 will certainly push forward the idea of improved protection of laying hen

flocks against outside environmental effects and strongly suggest the use of indoor husbandry

systems rather than aviaries with outdoor access or free range systems. Therefore, the recent

development of small aviary systems will most probably play a major in the German laying

hen industry in the near future.

The objective of the current study was to evaluate different types of house keeping systems

for laying hens with respect to layers’ welfare and health status, egg quality traits and

production parameters at two different experimental farms, comprising four different layer

lines. For the first time, perches within compartments of the small group system were

incorporated at different heights, thus meeting the legal requirements on the currently

approved small aviary system in this respect. Keeping hens in small group systems with

modified perch positions was directly compared to layers housed in small group systems with

non-elevated perches, furnished cages and an aviary system.

As the study was very comprehensive, it was split into two single dissertation projects.

Results deriving from the individual investigations together with data which had been

collected at the same trial farms from 1999-2004 and published by different authors, were

jointly analysed and discussed in the meta-analysis of this work. Table 1 provides a survey of

the different housing systems, perch positions and layer lines tested over two laying periods at

the two different experimental farms and refers to the main focal points analysed in the

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4

different chapters of this work. Chapter II provides an analysis of bone strength, keel bone

status and egg characteristics of Lohmann Silver and Lohmann Tradition hybrids kept in

furnished cages and small group systems with non-elevated perches in comparison to an

aviary system. In Chapter III, the effect of small group systems with elevated perch

configurations on bone traits, egg quality and production parameters in LS layers was

evaluated. Chapter IV illuminates the impact of different perch configurations and group sizes

within modified small group systems and furnished cages in Lohmann Brown and Lohmann

Selected Leghorn layers on humerus and tibia bone strength. In Chapter V, heterophil to

lymphocyte ratio (H/L-ratio), which reflects a measure of stress perception in laying hens was

analysed in LS layers. Chapter VI provides an analysis of a macroscopic and histological

assessment of keel bone. The general discussion is conducted in form of a meta-analysis in

Chapter VII. A summary of this work is provided in Chapter VIII, followed by an extended

German summary in Chapter IX.

Table 1: Brief overview of the experimental design of this study and the main focal points analysed in the different chapters of this work

Comparison of six housing systems for laying hens Evaluation of effects Aviplus

(FC) EV 625a-EU

(SG) EV 625A-EU

(FC) Natura

(Aviary) Conventional

cages Intensive free range

Farm A First laying period

Perch positions original original - original

LS/LT layers: Humerus and tibia strength, keel bone status, egg quality traits (Chapter II)

Farm A Second laying period

Perch positions original modified - original

LS layers: Humerus strength, tibia strength, keel bone status, egg quality traits, laying performance (Chapter III); Stress perception (heterophil/lymphocyte ratio) (Chapter V)

Farm B First and second laying period

Perch positions original modified modified -

LSL/LB layers (first laying period) and LSL layers (second laying period): Humerus strength, tibia strength, keel bone status, laying performance (Chapter IV)

Former experimental data included in a meta-analysis with special focus on: Humerus and tibia bone strength, keel bone status, plumage condition, food pad health, egg shell strength, laying performance, mortality and behaviour (Chapter VII)

Farm A and B All laying periods tested

LS/LT/LSL/LB layers: histological evaluation of keel bone (Chapter VI) FC: furnished cages, SG: small group system, LS: Lohmann Silver, LT: Lohmann Tradition, LSL: Lohmann Selected Leghorn, LB: Lohmann Brown

Chapter II

Evaluation of bone strength, keel bone deformity and egg quality

of laying hens housed in small group housing systems and

furnished cages in comparison to an aviary housing system.

B. Scholz, S. Rönchen, H. Hamann and O. Distl

Archiv für Tierzucht

Chapter II: Bone strength, keel bone status and egg quality in LSL and LB layers

Institute for Animal Breeding and Genetics, University of Veterinary Medicine Hannover,

Bünteweg 17p, 30559 Hannover, Germany

Britta Scholz, Swaantje Rönchen, Henning Hamann and Ottmar Distl

Evaluation of bone strength, keel bone deformity and egg quality of laying hens housed

in small group housing systems and furnished cages in comparison to an aviary housing

system

Evaluierung des Einflusses von Kleingruppenhaltung und ausgestaltetem Käfig im

Vergleich zu einer Volierenhaltung auf Knochenfestigkeit, Brustbeinstatus und

Eiqualität bei Legehennen

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Abstract

The objective of the study was to assess bone breaking strength, keel bone status and egg

quality parameters of Lohmann Silver (LS) and Lohmann Tradition (LT) layers housed in

small group systems (SG) and furnished cages (FC) in comparison to an aviary system. At the

end of the 3rd, 6th, 9th and 11th laying month, approximately 40 hens were randomly chosen

from each housing system and slaughtered (478 hens in total). Humerus and tibia strengths

were analysed using a three-point-bending machine. Keel bone status was evaluated on a

scale from 1 (severe) to 4 (no deformity). Shell breaking strength was measured every four

weeks, totalling 4,887 eggs. Statistical analyses were performed using the MIXED procedure

of SAS. Humerus and tibia strengths of LS layers housed in SG were significantly higher

compared to LS hens kept in FC. Bone breaking strengths of humerus and tibia in LS and LT

layers were highest in the aviary system and the differences to the other housing systems were

significant. No significant differences in tibia and humerus bone breaking strengths were

found between SG and FC for LT hens. Keel bone status was not significantly influenced by

housing system or laying strain. For both hybrids, shell breaking strength was significantly

lower in SG compared to FC and aviary system. The results showed that SG systems can

significantly enhance bone breaking strength for LS layers in comparison to hens kept in FC.

The lower shell breaking strength of eggs in SG might slightly impair economic aspects.

Key Words: laying hens, bone strength, keel bone status, egg quality, housing systems

Zusammenfassung

Ziel der vorliegenden Studie war es, Humerus- und Tibiabruchfestigkeiten, Brustbeinstatus

sowie ausgewählte Parameter zur Eiqualität der Legelinien Lohmann Silver (LS) und

Lohmann Brown (LB) aus ausgestaltetem Käfig (FC) und Kleingruppenhaltung (SG) im

Vergleich zu einer Volierenhaltung zu untersuchen. Am Ende des 3., 6., 9. und 11.

Legemonats wurden jeweils 40 Hennen aus den drei Haltungssystemen entnommen und

geschlachtet (insgesamt 478 Tiere). Die Knochenbruchfestigkeiten wurden mittels einer

Materialprüfmaschine gemessen. Der Brustbeinstatus wurde anhand einer Skala von 1

(hochgradig verändert) bis 4 (ohne besonderen Befund) beurteilt. Untersuchungen zur

Eiqualität wurden während der Legeperiode in einem Abstand von vier Wochen durchgeführt

(insgesamt 4.887 Eier). Die statistische Auswertung erfolgte mit der Prozedur MIXED von

SAS. Humerus- und Tibiafestigkeiten der LS Hennen aus SG waren signifikant höher im

Vergleich zu LS Hennen aus FC. Für beide Legelinien erwiesen sich die in der

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Volierenhaltung gemessenen Humerus- und Tibiafestigkeiten im Vergleich zu den zwei

übrigen Haltungsformen signifikant am höchsten. Für die LT Hennen konnte kein

signifikanter Unterschied in der Humerus- und Tibiaknochenfestigkeit zwischen SG und FC

ermittelt werden. Der Brustbeinstatus wurde nicht signifikant von Haltungssystem oder

Legelinie beeinflusst. Die Eischalenfestigkeit war für beide Legelinien in SG signifikant

niedriger verglichen zu FC und Volierenhaltung. Die Ergebnisse zeigten, dass die

Kleingruppenhaltung die Knochenfestigkeit von LS Hennen im Vergleich zu Hennen aus

ausgestaltetem Käfig signifikant verbessern konnte. Die niedrigere Schalenfestigkeit aus SG

könnte sich möglicherweise negativ auf die Wirtschaftlichkeit dieses Haltungssystems

auswirken.

Schlüsselwörter: Legehennen, Knochenfestigkeit, Brustbeinstatus, Eiqualität,

Haltungssysteme

Introduction

Since animal welfare plays an increasing role for the consumer, political decisions on laying

hen husbandry have become a focal point in the European Union. Due to current legal

regulations, conventional cages have to be replaced by alternative housing systems or

furnished cages by the end of 2011 in all European countries. In Germany, conventional cages

will be forbidden after 2008 and furthermore, furnished cages will be abandoned after 2011

also. Research is strongly required to test small group housing systems, which are currently

discussed to replace furnished cages by the end of 2011, thus offering an option to alternative

housing systems. Small group systems are designed to house larger groups of hens per

compartment and to provide an enriched environment with help of perches, nest box, sand

bath and devices to shorten claws. They aim to combine improved animal welfare with the

positive hygienic aspects, such as reduced risk of zoonoses and infections that are related to

house keeping systems which are well protected from outside environmental influences. So

far, health and welfare issues of hens housed in small group systems have not been directly

compared to layers housed in an aviary system. The objective of the present investigation was

to assess bone breaking strength, keel bone deformity and egg quality of Lohmann Silver (LS)

and Lohmann Tradition (LT) laying hens housed in a small group housing system (Eurovent

625a-EU) and furnished cages (Aviplus) in direct comparison to an aviary housing system

(Aviary “Natura”).

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Materials and methods

All three housing systems examined (provided by Big Dutchman, Vechta, Germany) were

established within separate rooms of one experimental building. The furnished cage system

Aviplus (FC) consisted of a three-tier block of double-sided cages with solid side and rear

partitions. Group sizes comprised 10 layers (bottom tier), 20 layers (second tier) and 30 hens

(top tier). The small group housing system Eurovent 625a-EU (SG) was built without a centre

partition and accommodated group sizes of 40 and 60 laying hens which were evenly

distributed over the three levels. In both systems, each compartment was equipped with

perches, litter bath, nest box and claw shortening devices. Perches were incorporated in

parallel position to the length of each compartment. In SG, the central tube for the automatic

distribution of the dust bathing substrate served as additional perching space. The cage

surface area provided was 750 cm² per hen. The EU legislative standards on keeping laying

hens (EU directive 1999/74/EG) were fully met (Tab. 1). The aviary system (model “Natura”)

was equipped with a three tier central block and provided access to a covered outdoor area. It

consisted of two compartments, each containing 1,215 laying hens. Perches were installed in

front of the second level and above the top level. Family nest boxes were attached on the

walls opposite the central block. They were connected via footboards with the medium level

of the system.

Table 1 Brief description of the three different housing systems tested FC SG Aviary Group size 10 20 30 40 60 1215 Floor space (mm x mm)

1,206 x 625

2,412 x 625

3,618 x 625

2,412 x 1,250

3,618 x 1,250

7,050 x 18,386

Height (mm) 450 450 450 450 450 2,350 (c.b.) Space/hen (cm²) 756 756 756 750 750 approx. 1,067

FC: furnished cage system Aviplus; SG: small group system Eurovent 625a-EU; c.b.: central block of aviary system.

The trial investigated started in July 2004 and ended in July 2005. Two floor-reared, brown

layer lines (Lohmann Tradition (LT) and Lohmann Silver (LS)) were transferred to the three

housing systems at the age of 18 weeks. Each system tested contained approximately 1,500

layers. All laying hens were subjected to identical management conditions. A common 2-

phase diet for laying hens (Bela-Mühle, Vechta, Germany) was fed 3 to 4 times a day. On

average, food contained 10.8 MJ ME, 3.53 % calcium and 0.49 % total phosphorus. Water

was supplied ad libitum via nipple drinkers. In all three housing systems tested, the light

9


period was gradually stepped up from 10.5 h (week 18) up to 14 h (week 26 until the end of

the laying cycle).

At the end of the 3rd, 6th, 9th and 11th laying month approximately 40 hens were randomly

chosen from each housing system (considering layer strain and group size to equal numbers)

and slaughtered (478 hens in total). Humerus and tibia bones were removed from muscles and

tendons and stored for one day (+ 4°C) until bone strength analysis. Bone breaking strength

(N) was measured by using a three-point-bending machine (“Zwick/Z2,5/TNIS”, Zwick-

Roell, Ulm, Germany). Bone ends were placed on two supports and a constant, perpendicular

force was applied until bone fracture.

The keel bone status of the layers was evaluated visually and per palpation after removal of

the skin. It was recorded on a scale from 1 to 4 (1 = severe deformity, 2 = moderate

deformity, 3 = slight deformity, 4 = no deformity).

With begin of the third laying month, every four weeks a sample of approximately 150 and

every 12 weeks a sample of approximately 300 eggs (totalling 4,887) was collected. Shell

breaking strength (N) was assessed using the test machine “Zwick/Z2,5/TNIS”. Eggshell

thickness (µm) was defined using a micrometer (QCT from TSS, York, UK). Eggshell density

(mg/cm²) was calculated by dividing shell weight by surface area. Albumen height (mm) was

measured with help of a semi-automatic device (QCH from TSS, York, UK) and converted to

Haugh Units. Results were recorded separately for housing system, layer line, group size and

compartment (SG).

Statistical analyses were performed using the MIXED procedure of the SAS package, version

9.1.3 (Statistical Analysis System Institute Inc., Cary, NC, USA, 2006). Traits were analysed

for the fixed effects of housing system, layer line, group size and laying month. Two-way and

three-way interactions were also tested. The interaction between laying month and individual

compartment was treated as a randomly distributed effect. The model for keel bone status and

bone breaking strength included body weight of the hens as a linear covariate.

Model for bone breaking strength

Yijklmno = µ + SYSi + LLj + GR(SYS)ik + MONl + SYS*LLij + SYS*MONil + LL*GR(SYS)ijk

+ b x BW(LL*MON)jlm + MON*COMP(LL*GR(SYS))ijkln + eijklmno

Yijklmno humerus or tibia bone breaking strength

µ model constant

SYSi fixed effect of housing system (i = 1-3)

10


LLj fixed effect of layer line (j = 1-2)

GR(SYS)ik fixed effect of group size within housing system (k = 1-6)

MONl fixed effect of laying months tested (l = 1-4)

SYS*LLij fixed effect of the interaction between housing system and layer line

SYS*MONil fixed effect of the interaction between housing system and laying month

LL*GR(SYS)ijk fixed effect of the interaction between layer line and group size within

housing system

b linear regression coefficient

BW body weight of hens before slaughter

MON*COMP(LL*GR(SYS))ijkln random effect of interaction between laying month and

compartment of housing system within layer line, group size and

housing system eijklmn random error

Model for keel bone status

Yijklmno = µ + SYSi + LLj + GR(SYS)ik + MONl + SYS*LLij + SYS*MONil + b x

BW(LL*MON)jlm + MON*COMP(LL*GR(SYS))ijkln + eijklmno

Model for egg quality traits

Yijklmn = µ + SYSi + LLj + GR(SYS)ik + MONl + SYS*LLij + SYS*MONil +

MON*COMP(LL*GR(SYS))ijklm + eijklmn

Yijklmn egg quality traits: shell breaking strength, shell thickness, shell density,

Haugh Units, egg weight

Results

Table 2 illustrates the least square means (LSM), standard errors (SE) and error probabilities

of variance analysis of bone breaking strength and keel bone status of hens housed in the three

different housing systems.

11


Table 2 Least square means (LSM) and their standard errors (SE) for bone breaking strength and keel bone status for the different housing systems and error probabilities (p) between housing systems

FC (I) SG (II) Aviary (III) p Trait LSM SE LSM SE LSM SE I-II I-III II-III

Humerus (N) 170.9 4.7 185.7 4.8 287.6 9.0 * *** *** Tibia (N) 115.8 2.0 121.9 2.0 156.5 3.4 * *** *** Keel bone (1-4) 3.54 0.06 3.51 0.06 3.43 0.09 n.s. n.s. n.s.

FC: furnished cage system Aviplus; SG: small group system Eurovent 625a-EU; n.s.: not significant, p > 0.05; *: p ≤ 0.05; ***: p ≤ 0.001.

Tibia and humerus breaking strengths of layers were highest in the aviary system. The

differences to both the furnished and small group housing system were significant. In

comparison to FC, bone breaking strengths of hens kept in SG were significantly higher. Keel

bone status was scored highest in FC, but statistically significant differences could not be

detected between the three different housing systems. Table 3 presents LSM and SE of bone

breakings strengths and keel bone status of the two different laying lines and error

probabilities between housing systems.

Table 3 Least square means (LSM) and their standard errors (SE) for bone breaking strength and keel bone status by different laying lines and housing systems and their error probabilities (p)

FC: furnished cage system Aviplus; SG: small group system Eurovent 625a-EU; LS: Lohmann Silver; LT: Lohmann Tradition; n.s.: not significant, p > 0.05; **: p ≤ 0.01; ***: p ≤ 0.001.

FC (I) SG (II) Aviary (III) p Trait LSM SE LSM SE LSM SE I-II I-III II-III

Humerus LS (N) 159.5 6.6 185.6 6.7 293.8 12.7 ** *** *** Humerus LT (N) 182.3 6.5 185.7 6.7 281.3 12.7 n.s. *** *** Tibia LS (N) 109.1 2.8 120.0 2.8 156.3 4.8 ** *** *** Tibia LT (N) 122.4 2.7 123.8 2.8 156.6 4.9 n.s. *** *** Keel bone LS (1-4) 3.5 0.1 3.4 0.1 3.4 0.1 n.s. n.s. n.s. Keel bone LT (1-4) 3.6 0.1 3.7 0.1 3.5 0.1 n.s. n.s. n.s.

Humerus and tibia breaking strengths of LS layers were significantly higher in SG compared

to the FC. However, bone strengths of hens housed in the aviary system were significantly

higher to both the SG and FC system. No differences in humerus and tibia bone breaking

strengths could be detected for LB layers housed in the SG and FC, whereas differences

between the aviary and the other two systems were significant. Keel bone status within laying

line did not differ significantly between the three housing systems tested. Table 4 presents

LSM and SE of keel bone status of the different laying months tested. Results of keel bone

12


status in the 11th laying month differed significantly from findings in the 6th laying month,

thus reflecting an increase of deformities towards the end of the laying period in all housing

systems tested.

Table 4 Least square means (LSM) and their standard errors (SE) for keel bone status of each housing system and laying month and error probabilities (p) among laying months within each housing system

Laying month p Keel bone status (1-4) 3 6 9 11 3-6 3-9 3-11 6-9 6-11 9-11FC 3.8 ± 0.1 3.8 ± 0.1 3.1 ± 0.1 3.4 ± 0.1 n.s. *** n.s. *** * n.s.SG 3.3 ± 0.1 3.8 ± 0.1 3.5 ± 0.1 3.4 ± 0.1 * n.s. n.s. n.s. * n.s.Aviary 3.7 ± 0.2 3.7 ± 0.2 3.2 ± 0.2 3.2 ± 0.2 n.s. n.s. * n.s. * n.s.

FC: furnished cage system Aviplus; SG: small group system Eurovent 625a-EU; n.s.: not significant, p > 0.05; *: p ≤ 0,05; ***: p ≤ 0.001; LS: Lohmann Silver; LT: Lohmann Tradition.

Least square means (LSM) and standard errors (SE) of the egg quality traits investigated for

the different housing systems are presented in table 5.

Table 5 Least square means (LSM) and their standard errors (SE) for egg quality traits and error probabilities (p) between housing systems

FC SG (II) Aviary (III) p Trait LSM SE LSM SE LSM SE I-II I-III II-III

Shell strength (N) 40.7 0.3 39.6 0.2 40.6 0.3 ** n.s. ** Shell thickness (µm) 343.6 0.8 342.3 0.8 346.1 1.3 n.s. n.s. ** Shell density (mg/cm²) 87.9 0.2 86.6 0.2 87.7 0.3 *** n.s. ** Haugh Units 79.4 0.2 80.8 0.2 80.5 0.3 *** ** n.s. Egg weight (g) 64.9 0.1 64.4 0.1 65.2 0.1 ** n.s. *** FC: furnished cage system Aviplus; SG: small group system Eurovent 625a-EU; n.s.: not significant, p > 0.05; **: p ≤ 0.01; ***: p ≤ 0.001.

Shell breaking strength, shell density, shell thickness and egg weight were significantly higher

in the aviary system compared to SG. All egg quality traits presented except shell thickness

turned out to be significantly higher in the FC in comparison to SG. Haugh Units measured in

the aviary and SG did not differ significantly and exceeded Haugh Units recorded in FC.

Discussion

Egg shell breaking strength can be regarded as a trait of major commercial importance. A

high incidence of cracked eggs easily spoils financial gains. Literature findings on egg shell

breaking strength are very diverse. Some authors described an increased shell breaking

13


strength in aviary systems, whereas other studies did not detect differences of shell breaking

strength between cage and alternative housing systems (VAN DEN BRAND et al., 2004). In

the present investigation, the lowest shell breaking strength was found in the SG (39.6 N).

Compared to a study by LEYENDECKER et al. (2005), shell breaking strengths of LS hens

kept in an aviary (38.1 N) and furnished cage system (36.6 N) were exceeded by the present

findings. In an investigation by VITS et al. (2005) egg quality of layers housed in two

different small group systems was compared to furnished cages. The small group systems

reflected a tendency to improve egg shell breaking strength. In the present study egg shell

strength could not be increased by layers kept in the SG system, but compared to findings in

earlier investigations, the shell breaking strength measured met a high egg quality standard. In

a study by WHITEHEAD (2004) it is discussed that hens with a favourable predisposition of

stronger bones provide less calcium for egg shell formation. This might be part of an

explanation for the lower shell breaking strength of eggs found in SG compared to the other

two systems. Bone strength of hens in SG was stimulated in comparison to FC. Hence,

calcium might be preferentially used for bone remodelling and conservation rather than for

egg shell composition. Haugh Units serve as a well-known parameter to determine egg

freshness. The value decreases with extended time of storage and rising temperature. In the

present study, Haugh Units turned out to be highest in the SG system. It is difficult to

interpret this result as eggs of the three housing systems were treated under identical

conditions from the point of collection until egg quality tests. Literature references regarding

the impact of housing system on Haugh Units are very few and contradictory. Some authors

reported higher Haugh Units in conventional cages (SCHOLTYSSEK, 1975) compared to

floor keeping systems, whereas other findings stated the opposite. Nevertheless, the present

result underlines the high quality of eggs stemming from LS and LT hens kept in small group

housing systems.

With reference to health and welfare issues, osteoporosis of layers is one of the major

concerns related to conventional cages. In a variety of studies on furnished cages, the

incorporation of perches served to improve bone strength of layers (ABRAHAMSSON et al.,

1993). Small group housing systems are designed to ameliorate bone strength by the provision

of perches together with a larger floor space. VITS et al. (2005) compared bone strengths of

layers kept in a small group housing system and furnished cages. Humerus strength was found

to be higher in the furnished cage system, whereas tibia strength did not differ significantly

between the systems. Bone strengths were clearly increased compared to conventional cages.

In the current investigation, humerus and tibia strengths of LS hens kept in SG significantly

14


exceeded bone strengths measured in FC. Humerus and tibia strengths of LT kept in SG

showed a tendency to improved bone strengths compared to FC. Nevertheless, bone strengths

measured in the aviary system were not reached. Humerus bone strength of hens housed in

SG clearly exceeded bone strength reported by LEYENDECKER et al. (2005) for LS layers

kept in furnished cages (129.6N). Tibiae strengths between these two investigations hardly

differed. This result corresponds to other findings in the literature. The impact of a housing

system on tibia bone strength has often been reported to be less distinct compared to humerus

bone strength (VITS et al., 2005; HUGHES et al., 1993). In a study by BISHOP et al. (2000)

the inheritance of bone strength characteristics was revealed. Sole selection on improved bone

strength would have inevitably resulted in increased body weight. In the present study hens in

the aviary system had the strongest bones and showed the lowest mean body weight (1994g)

compared to hens kept in SG (2067g) and FC (2073g). The provision of more space together

with the incorporation of perches in the aviary and small group housing system enabled hens

to perform more movements. As a result, bone strength was stimulated and body weight was

reduced within physiological limits.

The type of housing system does not only influence bone strength but also affects the status of

keel bone. Due to its exposed anatomical location, keel bone is very vulnerable to

deformations. Accidental collisions with compartment equipment, extended perching and the

resulting compression are likely to impact keel bone condition. Deformities seem to be

strongly associated with the incorporation of perches. APPLEBY et al. (1993) described a

significantly higher incidence of keel bone deformations of hens kept in furnished cages

compared to conventional cages. FREIRE et al. (2003) detected old keel fractures in 73% of

birds kept in aviary systems. Thus, hens in aviary systems and furnished cages are mostly

predisposed to produce keel bone alterations. Keel bone deformities become manifest in the

form of twists, osteal proliferations and dorso-ventral compressions. FLEMING et al. (2004)

detected fracture callus material in all cases of deformities. In the present study, keel bone

status of hens in the aviary system tended to be lower scored compared to SG and FC at the

end of the laying period. In SG, the lowest-rated keel bone conditions were recorded in the

3rd and 11th laying month. Keel bone might not have been fully ossified in the 3rd laying

month and therefore being very vulnerable to external influences. Also, it might have taken a

longer time for hens to establish a social ranking within a group size of 40 or 60 hens

compared to the smaller group sizes of FC. This might have led to more agitation, thus

causing collision with perches. A study by KEELING et al. (2003) indicated that intermediate

group sizes between 30 and 60 hens suffer from a high degree of social disruption. In all

15


housing systems tested, keel bone status significantly deteriorated from the 9th to the 11th

laying month. No statistically significant differences of keel bone status could be found

between the three housing systems at the end of the laying period.

The current study showed that the development of small group housing systems seems to be a

well suitable option to alternative housing systems. In SG, internal and external egg quality

met a high qualitative standard together with the other two systems tested. For a more

comprehensive evaluation of economic parameters, the amount of dirty and cracked eggs

should be analysed together with data on egg production. With reference to bone strength,

results on improved bone breaking strengths of hens housed in SG compared to layers in FC

are very promising. The provision of more space due to larger group sizes seems to affect

bone strength in a very positive way. Further research would be suggested on cage equipment,

particularly perches. As the incorporation of perches is closely linked with both increased

bone strength and the incidence of keel bone deformities, research should be stimulated in

order to optimise these two parameters.

References

ABRAHAMSSON, P.; TAUSON, R.: Effect of perches at different positions in conventional

cages for laying hens of two different strains. Acta Agric. Scand., Sect. A, Animal Sci. 43

(1993), 228-235

APPLEBY, M.C.; SMITH, S.F.; HUGHES, B.O.: Nesting, dust bathing and perching by

laying hens in cages: effects of design on behaviour and welfare. Br. Poult. Sci. 34 (1993),

835-847

BISHOP, S.C.; FLEMING, R.H.; MCCORMACK, H.A.; FLOCK, D.K.; WHITEHEAD,

C.C.: The inheritance of bone characteristics affecting osteoporosis in laying hens. Poult. Sci.

41 (2000), 33-40

FLEMING, R.H.; MCCORMACK, L.; MCTEIR, L.; WHITEHEAD, C.C.: Incidence,

pathology and prevention of keel bone deformities in the laying hen. Br. Poult. Sci. 45 (2004),

320-330

FREIRE, R.; WILKINS, L.J.; SHORT, F.; NICOL, C.J.: Behaviour and welfare of individual

laying hens in a non-cage system. Br. Poult. Sci. 44 (2003), 22-29

HUGHES B.O.; WILSON, W.; SMITH, S.F.: Comparison of bone volume and strength as

measures of skeletal integrity in caged laying hens with access to perches. Res. Vet. Sci. 54

(1993), 202-206

16


17

KEELING, L.J.; ESTEVEZ, I.; NEWBERRY, R.C.; CORREIA, M.G.: Production-related

traits of layers reared in different sized flocks: the concept of problematic intermediate group

sizes. Poult. Sci. 82 (2003), 1393-1396

LEYENDECKER, M.; HAMANN, H.; HARTUNG, J.; KAMPHUES J.; NEUMANN, U.;

SÜRIE, C.; DISTL, O.: Keeping laying hens in furnished cages and an aviary housing system

enhances their bone stability. Br. Poult. Sci. 46 (2005), 536-544

SCHOLTYSSEK, S.: Die Qualität von Eiern aus Käfig- und Bodenhaltung. Arch. Geflügelk.

2 (1975), 59-62

VAN DEN BRAND, H.; PARMENTIER, H.K.; KEMP, B.: Effects of housing system

(outdoor vs cages) and age of laying hens on egg characteristics. Br. Poult. Sci. 45 (2004),

745-752

VITS, A.; WEITZENBÜRGER, D.; HAMANN, H.; DISTL, O.: Production, egg quality,

bone strength, claw length, and keel bone deformities of laying hens housed in furnished

cages with different group sizes. Poult. Sci. 84 (2005), 1511-1519

WHITEHEAD, C.C.: Overview of bone biology in the egg-laying hen. Poult.Sci. 83 (2004),

193-199

Britta Scholz, Swaantje Rönchen, Dr. Henning Hamann, Prof. Dr. Dr. Ottmar Distl*



*Corresponding author: O. Distl

E-mail: [email protected]

Chapter III

Bone Strength, Keel Bone Deformities and Egg Quality of

Lohmann Silver Layers Kept in Small Group Systems with

Modified Perch Positions in Direct Comparison to an Aviary

Housing System and Furnished Cages


Chapter III: Bone traits and egg quality in small group, furnished and aviary system

LOHMANN SILVER HENS KEPT IN SMALL GROUP SYSTEMS

Bone Strength, Keel Bone Deformities and Egg Quality of Lohmann Silver Layers Kept

in Small Group Systems with Modified Perch Positions in Direct Comparison to an

Aviary Housing System and Furnished Cages

B. Scholz1, S. Rönchen, H. Hamann and O. Distl

Institute of Animal Breeding and Genetics, University of Veterinary Medicine Hannover,


1Corresponding author:

Britta Scholz, Insitute of Animal Breeding and Genetics, University of Veterinary Medicine

Hannover, Bünteweg 17p, 30559 Hannover, Germany, Tel.: 0049-511-953-8878; Fax: 0049-

511-953-8582; e-mail: [email protected].

20


ABSTRACT The objective of the current investigation was to assess the influence of a small

group housing system (Eurovent (EV) 625a-EU, equipped with elevated perches, group sizes

40, 60 layers), furnished cages (Aviplus, group sizes 10, 20, 30 hens) and an aviary system

(Natura, 2 pens, 1250 hens) on bone strength, keel bone deformities and egg quality traits of

Lohmann Silver (LS) layers under identical management and feeding conditions.

Compartments of EV 625a-EU were equipped with perches at different heights (two variants).

Investigations were carried out in the 3rd, 6th, 9th and 12th laying month, comprising a total

of 432 hens. Humerus bone strength did not differ between EV 625a-EU and Aviplus,

whereas tibia bone strength was significantly stronger in EV 625a-EU compared to Aviplus in

the 12th laying month. Hens kept in the aviary system consistently reflected significantly

stronger humerus and tibia bones. Group sizes within EV 625a-EU and Aviplus had a

significant effect on humerus and tibia bone strength. Hens kept in group sizes of 40 hens (EV

625a-EU) and 20 hens (Aviplus) showed highest bone strengths. The different perch variants

within compartments of EV 625a-EU did not have a significant effect on bone strength. Keel

bone deformities of hens kept in the aviary system were significantly more often registered

compared to hens housed in EV 625a-EU and Aviplus. Layers kept in compartments of EV

625a-EU with the back perches being heightened showed significantly more often deformed

keel bones compared to hens housed in Aviplus. Keel bone condition was not influenced by

different group sizes. Egg quality was spoiled in EV 625a-EU due to significantly higher

percentage of dirty and cracked eggs. The small group system with elevated perches did

improve tibia bone strength of LS hybrids compared to furnished cages even if being not

comparable to hens kept in the aviary system. The unfavorable keel bone status related to

hens kept in aviary systems could be largely prevented.

Key words: Small group system, furnished cages, bone strength, keel bone status, egg

quality.

INTRODUCTION

Due to the EU Council directive 1999/74/EC (CEC, 1999) on laying down minimum

standards for the protection of laying hens, conventional cages will be phased out within the

EU by the end of 2011 and replaced by furnished cages. In contrast to other EU countries, the

German government has put a ban on conventional cages by the end of 2008 already.

Furthermore, furnished cages will have to be substituted by either alternative systems or the

recently approved small group housing systems with elevated perches from January 2012.

Therefore, research on the development of small group housing systems with modified perch

21


positions is strongly required as these systems will play an important role in the future of

laying hen husbandry in Germany. Small group housing systems are designed to keep group

sizes of up to 60 laying hens per compartment, thus offering hens a larger floor space and

increased possibilities to increased social interaction. One of the major advancements is the

arrangement of perches on at least two different levels within each individual compartment.

This improvement aims at reducing the risk of inactivity osteoporosis in laying hens, which

has been a great welfare concern (Baxter, 1994) and has brought up discussions on legal

changes in laying hen husbandry. In several studies, the implementation of perches (furnished

cages, small group housing systems, aviary systems) has succeeded in improving bone

strength in layers (Hughes and Appleby, 1989; Barnett et al., 1997; Leyendecker et al., 2005).

Perches installed at different heights are supposed to further increase bone strength in layers

by stimulating movement and performance of natural behavioral traits. In correspondence to

furnished cages, small group housing systems are also enriched with nest boxes, sand baths

and devices to shorten claws. In contrast to alternative housing systems, small group systems

are designed to bring together improved animal welfare with the positive hygienic aspects that

are associated with house keeping systems which are well safeguarded against outside

environmental influences. The objective of the current investigation was to draw a direct

comparison of bone breaking strength, keel bone status, egg quality and production

parameters of Lohmann Silver (LS) layers kept in small group housing systems with two

variants of perch positions, furnished cages and an aviary housing system. Special focus was

put on the different perch arrangements and group sizes of the small group housing system

and their effect on bone characteristics. The study was conducted under entirely identical

management conditions, which assures a high informational value due to a direct comparison

of the three house keeping systems tested. So far, health, welfare and production issues of

hens kept in small group housing systems with elevated perch positions have not been

described and directly compared to an alternative housing system and furnished cages.

MATERIALS AND METHODS

Housing Systems and Layer Line

The three housing systems (provided by Big Dutchman GmbH, Vechta, Germany) were

installed in 3 different rooms within the same experimental building. The small group housing

system Eurovent (EV) 625a-EU was installed over 3 tiers. It accommodated compartments of

40 and 60 laying hens (floor space: 2,412 x 1,250 mm and 3,618 x 1,250 mm), which were

evenly distributed over the 3 levels of the system. Each compartment of EV 625a-EU was

22


equipped with 2 next boxes (900 mm x 260 mm (60 hens) and 600 mm x 260 mm (40 hens)).

The furnished cage system Aviplus consisted of a three-tier double-sided block of

compartments with solid side and rear partitions. Group sizes comprised 10 layers (bottom

tier; floor space: 1,206 x 625 mm, 1 nest box per compartment), 20 layers (medium tier; floor

space: 2,412 x 625 mm, 2 nest boxes) and 30 hens (top level; floor space: 3,618 x 625 mm, 3

nest boxes). Compartments of both systems offered a height of 450 mm and were enriched

with perches, sand baths, nest boxes and devices to shorten claws. The aviary system

“Natura” provided a fully littered indoor floor space and consisted of a three-tier central

block, which was divided into 2 pens each containing 1,250 laying hens (floor space: 3,650 x

15,980 mm). Both pens were located within the same room and provided access to 2 separate,

covered outdoor areas (20,980 x 3,400 mm). Each pen of the aviary system was equipped

with 21 family next boxes (1,220 x 440 mm), which were attached alongside the walls

opposite the central block and could be accessed via footboards from the first and second tier

of the system. All 3 systems tested fully conformed to the EU legislative standards on keeping

laying hens (EU directive 1999/74/EC). The investigation comprised one laying period which

lasted from September 15th, 2005 until October 16th, 2006. Lohmann Silver hybrids used in

the study were brown layers, predominantly white-feathered and exhibited higher body

weight compared to more common brown layer lines, such as Lohmann Brown or Lohmann

Tradition.

Perch Positions within Housing Systems

In the small group housing system, 4 perches per pen were incorporated in parallel position to

the length of each compartment. Perches were installed at 2 different heights with either the

back perches being elevated (BE, 200 mm distance to cage floor) or back and front perch

being heightened (200 mm and 275 mm distance to cage floor) and installed in a stepped

position (ST) (figure 1). The central tube for the automatic distribution of dust bathing

substrate served as additional perching space. In EV 625a-EU, 4 compartment variants related

to the different group sizes and perch positions (60 hens, BE, ST and 40 hens BE, ST) with 2

replicates each per tier were tested. In the furnished cage system, back and front perch were

installed on an even level within each individual compartment (90 mm to cage floor).

Compartments tested had 8 replicates (top tier), 12 replicates (medium tier) and 24 replicates

(bottom tier). Perches were oval shaped with a flattened top and underside. They were 30 mm

thick and produced a contact area of 20.1 mm for the layers’ feet. All perches in the Aviplus

were made out of white, polished plastics (PVC, rigid). In EV 625a-EU, elevated perches

23


were made out of abraded, galvanized zinc and roundly shaped. In the aviary system, square

shaped wooden bars were incorporated in front of the medium level of the central block (830

mm to ground floor) and three galvanized perches were installed above the top level in a

stepped order (480 and 740 mm distance to top level).

Management and Feeding

All laying hens were subjected to identical management conditions throughout the trial

period. Hens were floor-reared within the same flock, thus ensuring fully identical rearing

conditions. Laying hens were treated according to a commonly accepted immunization

scheme for layers during the rearing and laying period. At the age of 18 weeks, a total number

of 5,500 Lohmann Silver hens was transferred to the experimental building and distributed to

the 3 house keeping systems. The lighting scheme employed comprised a 14 h light period in

all 3 housing systems. In the Aviplus and EV 625a-EU, light was provided from 5 am until 7

pm. The lighting period in the aviary system was adapted to environmental light variations

and comprised four different 14 h lighting periods throughout the trial period. The beginning

of the lighting period varied from 5 am (3rd laying month) up to 7.15 am (12th laying month).

Hens were fed a common 2-phase diet for layers, which was adapted to the stage of the laying

cycle. Food was automatically supplied via food chains 3 to 4 times a day. An analysis of

food components was conducted in regular intervals. On average, food contained 10.9 MJ

ME, 16.5% crude protein, 3.89% calcium and 0.48% total phosphorus. Water was supplied ad

libitum via nipple drinkers.

Analysis of Bone Breaking Strength

At the end of the 3rd, 6th, 9th and 12th laying month, approximately 36 laying hens were

randomly taken out of each housing system, considering group sizes and perch positions (EV

625a-EU) to equal parts. Investigations started at the end of the 3rd laying month in order to

give layers the opportunity to adapt to the different environmental housing conditions and

minimize a direct influence of floor-rearing conditions on the parameters tested. The study

comprised a total of 432 hens. Before slaughter, live weight of hens was measured.

Alternately the left or right humerus and tibia bones were dissected after removal of muscles

and tendons. Bones were stored for one day (+ 4°C) until bone strength analysis. Bone

breaking strength was measured by using a three-point-bending machine

(“Zwick/Z2.5/TNIS”, Zwick-Roell, Ulm, Germany). Bone ends were placed on two supports

24


(humerus: 40 mm, tibia: 90 mm distance) and a constant, perpendicular force was applied

until bone fracture. Bone strength was automatically recorded and measured in Newton (N).

Analysis of Keel Bone Status

Keel bone status of hens was macroscopically reported following the dissection of humerus

and tibia bones. After removal of the layers’ breast skin, keel bones were examined visually

and per palpation alongside the keel. According to the severity of deviations, keel bone status

was recorded on a scale from 1 to 4 (1 = severe deformity, 2 = moderate deformity, 3 = slight

deformity, 4 = no deformity). Keel bone deviations were observed in the form of s-shaped

deformities, osteal proliferations and dorso-ventral compressions.

Egg Quality Analysis and Investigation of Production Parameters

With begin of the 3rd laying month egg quality analysis was carried out every 4 weeks on 3

consecutive days. A sample of 120 eggs per housing system was randomly collected

considering group sizes, perch positions and compartments (EV 625a-EU) to equal parts. A

total number of 3,960 eggs was examined. Shell breaking strength was measured using the

test machine “Zwick/Z2.5/TNIS” and automatically recorded in Newton (N). Eggshell

thickness (µm) was reported using a micrometer (QCT from TSS, York, UK). Eggshell weight

(g) was measured after having dried the eggshells in a microwave. Eggshell density (mg/cm²)

was automatically calculated by dividing egg shell weight by egg surface area. Egg surface

area derived from the formula S = 4.67 x G2/3 (S: surface area, G: egg weight). Albumen

height (mm) was reported using a semi-automatic device (QCH from TSS, York, UK) and

automatically converted to Haugh Units (HU). Yolk color was measured on a scale from 1 to

15 using a yolk color fan (Roche, Switzerland). Meat and blood spots were recorded

separately and evaluated on a scale from 0 to 2 (0 = no meat/blood spot, 1 = meat/blood spot

smaller than 2 mm, 2 = meat blood spot larger than 2 mm). Hen egg production and the

number of cracked and dirty eggs were recorded on a daily basis. Daily egg mass was

calculated by multiplying the number of eggs laid per day by corresponding egg weight. Daily

salable egg mass did not include cracked and dirty eggs. Both parameters were related to the

number of hens present.

Statistical Analysis

Statistical analysis of the traits humerus and tibia bone breaking strength, keel bone status,

egg quality and body weight of layers was carried out using the Procedure MIXED of the

25


SAS package, version 9.1.3. (Statistical Analysis System Institute Inc., Cary, NC, USA,

2006). Housing system (SYS), group size within housing system (GR(SYS)), laying month

(MON), the interaction between housing system and laying month (SYS*MON) and perch

position (PP) within EV 625a-EU were included as fixed effects. The individual

compartments (comp) within housing systems were employed as randomly distributed effects.

Body weight (BW) within laying month was used as a covariate for the traits bone breaking

strength and keel bone status. F-test was conducted to test the significance of the effects in the

statistical model. A separate statistical analysis of data on the small group housing system was

carried out in order to test the fixed effect PP and results for the fixed and random effects as

parameterized in the model described above did not differ.

Yijklmno = µ + SYSi + GR(SYS)ij + MONk + SYS*MONik + PP(SYS)il + comp(SYS)im + b x

BW(MON)kn + eijklmno

Yijklmno humerus and tibia bone breaking strength/keel bone status

μ model constant

SYSi fixed effect of housing system (i = 1 to 3)

GR(SYS)ij fixed effect of group size within housing system (j = 1 to 6)

MONk fixed effect of laying month (k = 1 to 4)

SYS*MONik fixed effect of housing system and laying month (ik = 1 to 12)

PP(SYS)il perch positions within EV 625a-EU (l = 1 to 2)

comp(SYS)im randomly distributed effect of individual compartments within housing

systems (m = 1 to 70)


BW(MON)kn body weight of layers within laying month

eijklmno random error variation

Statistical analysis of cracked eggs (%), dirty eggs (%), produced eggs (%, per hen present),

egg mass and salable egg mass (g, per hen present) was carried out with a separate statistical

model in which housing system was included as a fixed effect and each day of lay was used as

a covariate in linear, quadratic, logarithmic and squared logarithmic form. Cracked and dirty

eggs were related to the total number of eggs laid throughout the laying period.

Residual correlations were calculated using the SAS procedure CORR for the residuals of the

traits analyzed with the above mentioned models excluding body weight of layers. Residuals

of traits were directly merged by individual laying hen.

26


RESULTS

Housing system had a significant effect on the traits humerus and tibia bone breaking

strength, keel bone status, blood spots, meat spots, egg weight, yolk weight and percentage of

dirty eggs. The different group sizes within housing system significantly impacted humerus

and tibia bone strength, blood spots and egg weight. Egg quality traits were significantly

influenced by laying month and the interaction between laying month and housing system.

(Table 1). Humerus and tibia bone breaking strengths were significantly higher in the aviary

system compared to hens kept in the small group system and furnished cages, whereas no

difference was found between the latter two systems (Table 2). Keel bone status was scored

significantly lower in the aviary system compared to EV 625a-EU and Aviplus. Hens kept in

Aviplus showed keel bones with less deformities compared to laying hens housed in EV

625a-EU, although differences did not achieve a significant level (p= 0.08).

The two different perch positions incorporated in the EV 625a-EU did not have a significant

effect on humerus and tibia bone breaking strengths and keel bone status within the small

group housing system, whereas hens kept in ST compartments of EV 625a-EU showed

significantly higher tibia bone breaking strength compared to hens kept in Aviplus. Keel bone

status of hens kept in the furnished cages was scored significantly higher compared to layers

housed in the small group housing system with perches being incorporated in the BE position

(Table 3).

With relation to the different group sizes, hens kept in Aviplus in pens of 20 layers had

significantly higher humerus and tibia bone strengths compared to hens housed in

compartments of 30 layers (Table 4). Group sizes comprising 10 hens had a significant

positive effect on tibia bone strength compared to the larger groups of 30 hens. In EV 625a-

EU, laying hens housed in compartments accommodating 40 hens had produced significantly

higher humerus bone strengths in comparison to group sizes of 60 layers. No difference

related to group sizes within EV 625a-EU was found for the traits tibia bone strength and keel

bone status.

Humerus and tibia bone strengths did not differ between Aviplus and EV 625a-EU related to

the different laying months tested except the 12th laying month (Table 5). Hens kept in the

EV 625a-EU had significantly higher tibia bone strength compared to Aviplus. In all four

laying months tested, humerus and tibia bone strengths of layers kept in the aviary system

were significantly higher compared to bone strengths of layers kept in Aviplus and EV 625a-

EU. Keel bone status differed between EV 625a-EU and Aviplus in the 9th laying month

when hens kept in the small group system reflected a significantly lower keel bone status

27


compared to layers housed in the furnished cage system. Keel bone status of hens kept in the

aviary system was scored significantly lower in the laying months 3 to 9 compared to hens of

Aviplus and significantly differed from hens kept in EV 625a-EU in the laying months 9 and

12.

Within Aviplus and EV 625a-EU, humerus bone strength did not differ among the different

laying months tested, whereas hens kept in the aviary system showed a significant decline in

humerus bone strength from the 3rd to the 12th laying month. Tibia bone breaking strength

did not differ among laying months in Aviplus, whereas a significant increase was observed

in EV 625a-EU and aviary system between the 3rd and 12th and 9th and 12th laying month.

Although the fixed effects MON and SYS*MON did not have an overall significant effect on

keel bone status, keel bone status within housing system was in most cases significantly lower

in the 3rd and 6th laying month when compared to laying month 9 and 12.

Body weight of layers was highest in Aviplus (2,085.9 g), followed by hens kept in the aviary

system (2,052.5 g) and EV 625a-EU (2,036.2 g), but differences did not achieve a significant

level.

A significant positive correlation was detected between residuals of the traits humerus and

tibia bone breaking strength. Residuals of the trait keel bone status reflected a significant

positive correlation with residuals of tibia bone strength, whereas no significant correlation

was found between residuals of keel bone status and humerus bone strength. Residuals of the

trait body weight were also significantly positive correlated with humerus and tibia bone

breaking strength (Table 6).

With relation to egg quality traits, no significant differences between housing systems was

found for the traits shell breaking strength, shell thickness, shell density, shell weight,

albumen height, Haugh units, yolk color and egg mass, whereas egg weight and the incidence

of meat and blood spots was significantly higher in Aviplus and EV 625a-EU compared to the

aviary system (Table 2). Egg and yolk weight were highest and daily salable egg mass was

lowest in EV 625a-EU and the differences to the aviary system (egg weight, daily salable egg

mass) and to the aviary system and Aviplus (yolk weight, daily salable egg mass) were

significant. The percentage of dirty eggs was significantly higher in EV 625a-EU compared to

Aviplus. Hens kept in the aviary system had produced significantly more dirty eggs than

layers housed in Aviplus. The percentage of cracked eggs in EV 625a-EU significantly

exceeded the proportion of cracked eggs in Aviplus and aviary system. Differences between

the latter two housing systems were also significant. Egg production (per hen present) was

significantly higher in the aviary system compared to EV 625a-EU and Aviplus. No

28


difference in egg production was found between the small group housing system and

furnished cages.

With relation to the different group sizes, egg weight of hens housed in groups of 10 and 20

layers (Aviplus) was significantly higher compared to groups of 30 layers (Table 4). Egg

quality traits measured in EV 625a-EU did not significantly differ among the group sizes of

40 and 60 layers. No significant differences in egg quality traits were found between the two

different perch positions tested in EV 625a-EU (Table 3).

DISCUSSION

Humerus bone breaking strength of hens kept in the small group system did not increase

compared to Aviplus. Previous studies have shown that the provision of perches at different

heights in non-commercial systems increased bone breaking strength of layers (Abrahamsson

et al., 1996). The results of the present study indicated that the incorporation of perches at

different heights together with larger group sizes in the EV 625a-EU might not have provided

enough stimuli to increase humerus bone strength compared to the furnished cage system. The

influence of the particular layer line LS should be considered when evaluating the results as

more commonly used layer lines might be more responsive to changes in bone strength due to

larger group sizes and variations in perch positions. Studies on hens kept in litter pens have

shown that perches which were incorporated in an elevated position were highly accepted

compared to non-elevated ones (Olsson and Keeling, 2000). In the current study, the design of

perches could have had a negative influence on layers’ perching behavior in EV 625a-EU. In

contrast to perches incorporated in the furnished cage system Aviplus, elevated perches

within compartments of EV 625a-EU were roundly shaped, which might have reduced their

usage. Duncan et al. (1992) described hens being more unstable on circular perches compared

to rectangular shaped ones. Knowles and Broom (1990) found layers kept in conventional

cages exhibiting the fewest limb movements and therefore having the weakest bones. Perches

at different heights within compartments of the EV 625a-EU might have inhibited hens’ limb

movements, particular wing flapping, as the arrangement of perches might have been

hindering. Norgaard-Nielsen (1989) found hens kept in cages being restricted in their wing

movements to a degree that bone strength was reduced. The author emphasized the

importance of height of compartments in order to allow movement in the three dimensions. In

the current study compartment heights of EV 625a-EU did not exceed compartment heights of

the furnished cage Aviplus, although perches had been installed at different heights. In an

investigation by Leyendecker et al. (2005), LS layers kept in furnished cages with group sizes

29


of 10 layers per compartment were compared to hens kept in an aviary system and the

differences related to humerus bone breaking strength were significant (furnished cage

system: 129.6 N, aviary system: 247.0 N). In the current study, humerus bone strength of hens

kept in EV 625a-EU (167.5 N) and Aviplus (166.6 N) clearly exceeded humerus bone

strength of LS hens kept in furnished cages measured by Leyendecker et al. (2005). These

results suggest that larger group sizes seem to have a positive impact on humerus bone

strength, although bone strengths of laying hens kept in the aviary system in both

investigations could not be achieved. In the current study, tibia bone strength measured in the

aviary system was significantly higher compared to EV 625a-EU and Aviplus. These results

do not agree with the findings of Taylor and Hurnik (1994), who did not detect differences in

tibia bone breaking strength between hens kept in battery cages and an aviary system.

Although the overall interaction SYS*MON was not significant, tibia bone breaking strength

of layers kept in EV 625a-EU measured in the 12th laying month was significantly higher

compared to hens kept in the furnished cages. These data support the tendency of a positive

impact of EV 625a-EU on tibia bone strength compared to Aviplus. The influence of different

housing systems on tibia bone strength has been described very inconsistently. Hughes and

Appleby (1989) described tibia bone strength being positively influenced by cage design as

soon as perches were long enough to provide perching space for simultaneous

accommodation of hens, whereas Moinard et al. (1998) and Hughes and Wilson (1993) could

not detect differences in tibiotarsal breaking strength due to different cage designs.

Comprising data of all four laying months tested, hens kept in EV 625a-EU with perches

being installed in the ST position had significantly higher tibia bone strength compared to

layers kept in the Aviplus. This result might be due to an increased mechanical loading on

tibia bone while jumping up and down elevated perches. In contrast to humerus bone strength,

tibia bone breaking strength differed within the small group housing system among the

different laying months tested and significantly increased from the 3rd to the 12th laying

month. These results are in correspondence with findings of Leyendecker et al. (2005), who

also detected an increase in tibia bone strength towards the end of the production cycle, while

humerus bone strength remained constant. Leyendecker et al. (2005) suggested an

accumulation of medullary bone in tibia together with little resorption of structural bone as a

possible explanation. Humerus bone strength of layers kept in Aviplus and EV 625a-EU

remained unchanged among the different laying months tested, thus demonstrating that layers

retained a constant level of humerus bone strength until the end of the laying cycle although

high egg production and therefore high Ca-requirements were present. Hens kept in the aviary

30


system experienced a significant decline in humerus bone strength between laying months 3

and 12, but humerus bone strength consistently exceeded bone strengths measured in Aviplus

and EV 625a-EU, which underlines the distinct impact of an alternative housing system on

bone breaking strength.

The different group sizes within EV 625a-EU and Aviplus had a significant effect on bone

strength and egg quality traits. Hens kept in the EV 625a-EU in compartments of 40 layers

had significantly higher humerus bone strength compared to pens of 60 hens. These findings

do not correspond with findings of Vits et al. (2005), who did not detect a significant effect of

group size on humerus and tibia bone breaking strengths in Lohmann Brown and Lohmann

Selected Leghorn layers. Keeling et al. (2003) described intermediate group sizes around 30

hens being problematic due to a high degree of social disruption and unstable social hierarchy

compared to group sizes of 15, 60 and 120 hens. In the compartments of 40 layers, unwanted

agitation due to stress and social conflicts might have increased general movements, which

could have resulted in increased humerus bone strength. According to Keeling et al. (2003)

hens kept in group sizes of 15 hens were able to maintain a stable hierarchy and groups of 60

and 120 layers reflected tolerant social behavior, thus exhibiting less social conflicts. A

possible social disruption in pens of 40 layers did not negatively impact egg quality, as no

differences in egg quality traits were found between the different group sizes in EV 625a-EU.

In Aviplus, hens kept in group sizes of 30 layers reflected lower humerus and tibia bone

strength compared to the smaller groups of 20 layers and 10 layers (tibia strength). Due to the

experimental design of the study, group sizes of 30 hens were kept in the third tier of the

Aviplus system. Previous studies have described hens being more fearful in upper tiers of a

housing system compared to lower tiers (Hemsworth and Barnett, 1989). One of the reasons

for lower humerus and tibia bone strength in groups of 30 layers might therefore be an

increased fear behavior in the upper tier, which could have negatively affected hens’ agitation

activities. Light intensity in all three housing systems was set to 20 lux, but its intensity

differed between the three tiers of Aviplus and EV 625a-EU with light being darker in the

bottom tier and brightest in the top tier. Although hens were observed to be more active with

higher light intensities (Boshouwers and Nicaise, 1987) and light is generally known to have a

positive impact on bone characteristics, the effect of a higher light intensity in the top tier of

Aviplus could not prevent a lower humerus and tibia bone breaking strength compared to the

medium and bottom tier of the system. The lower egg weight measured in groups of 30 layers

compared to compartments of 10 and 20 hens might have also been influenced by the

31


different tiers of the Aviplus system. Vits et al. (2006) reported lighter egg weight in upper

tiers of housing systems compared to medium levels.

With relation to keel bone status, a decline throughout the laying period, which was observed

in all three housing systems tested, was described by a variety of authors (Nicol et al., 2006;

Weitzenbürger et al., 2006a). Findings on inferior keel bone status of layers kept in the aviary

system agreed with previous studies. Freire et al. (2003) found a high number of keel bone

deviations in hens kept in perchery systems. In a study by Elson and Croxall (2006), keel

bone lesions were mostly prevalent in multi-tier aviary systems compared to conventional and

furnished cages. Accidental flight and landing collisions with perches were seen to be the

major reasons for keel bone deformities in aviary systems (Gregory et al., 1991). In a study on

furnished cages and furnished small group systems by Weitzenbürger et al. (2006a),

approximately 33 % of hens exhibited keel bone deformities during the laying period.

Abrahamsson and Tauson (1993) could relate the provision of perches to inferior keel bone

condition. In the present study, keel bone status of layers kept in EV 625a-EU did not differ

from layers kept in Aviplus except in the 9th laying month, when keel bone deformities were

significantly more often registered in the small group system. Fleming et al. (2004) found keel

bone deformities of hens being associated with a generally weaker skeleton. Although hens

kept in the small group system were offered a higher degree of movement and perching

stimulus, layers’ keel bone in general might be too weak and therefore not capable of being

positively influenced by different housing systems. The same applies to layers kept in the

aviary system. Hens exhibited a significantly unfavorable keel bone status compared to EV

625a-EU in the laying months 9 and 12. Tibia bone strength and keel bone status were

positively correlated in the present study, but neither the small group system nor the aviary

system did succeed in strengthening layers’ keel bone to an extent that it would withstand

accidental collisions with perches or mechanical pressure during perching activities.

Wahlström et al. (2001) made long-term perching activities together with increased

mechanical pressure on the keel responsible for a high incidence of keel bone deviations. As

hens kept in the small group system with perches being incorporated in the BE position even

exhibited a significantly poorer keel bone status compared to layers housed in Aviplus, a high

acceptance of elevated back and non-elevated front perch together with perching activities on

the central tube could have led to increased pressure on the keel bone. Perching on the

elevated back perch allowed hens to perch secludedly in the back of the compartment

compared to the elevated front perch of the ST perch variant. Frequent use of the round back

perch might have contributed to increased local pressure resulting in keel bone deformities,

32


which would be in correspondence with findings of Tauson and Abrahamsson (1994). As the

round perches incorporated in the ST position did not lead to unfavorable keel bone status

compared to Aviplus, the usage of the more exposed, elevated front perch might have been

less frequent and hens spent more time standing on the wire floor, thus relieving pressure on

their keel bone. In a study by Weitzenbürger et al. (2006b), hens kept in an Aviplus system

spent more time standing on the wire floor rather than using perches compared to layers kept

in two different Eurovent systems with perches at an even height. In the present study, layers

kept in Aviplus were also lacking the central tube as additional perching space. Therefore,

less perching activities in the furnished cage system could have explained the superior keel

bone status of hens kept in Aviplus compared to hens in the BE compartments of the small

group system. The arrangement of perches at different heights in a relatively high stocking

density (750 cm²/hen) could have also led to increased accidental collisions with perches. In

addition, elevated perches were of a darker color compared to the non-elevated ones in

Aviplus, which might have caused difficulties to approach perches properly. According to a

study on adequate perch distances within housing systems (Scott et al., 1997), perches should

be incorporated with minimized horizontal and vertical distances, thus ensuring a move

between perches without failures. The implementation of perches in the small group housing

system should have enabled hens to negotiate distances provided properly as maximum perch

distances from the cage floor did not exceed 275 mm.

With reference to egg quality parameters, a significant influence of housing system was

detected for the traits egg weight, yolk weight, percentage of dirty eggs, meat spots and blood

spots. Hens in the Aviplus and EV 625a-EU produced significantly heavier eggs compared to

layers kept in the aviary system. These results do not agree with findings of Van den Brand et

al. (2004). The authors found eggs from outdoor layers being relatively broader than eggs

from hens kept in cages, but indicated the problem of maintaining constant egg quality in

outdoor housing systems compared to battery cages. Taylor and Hurnik (1996) did not detect

differences in egg weight between hens kept in aviaries and conventional cages, thus

supporting the inconsistency on findings related to egg weight in previous studies. In the

current investigation, egg yolk weight might have accounted for the higher egg weight of hens

kept in the Aviplus and EV 625a-EU as these hens had produced eggs with significantly

higher yolk weights compared to layers kept in the aviary system. De Ketelaere et al. (2002)

found evidence that higher egg weight was not related to inferior egg shell breaking force. In

the current study, no significant influence of housing system on egg shell breaking force was

found, whereas egg weight significantly differed among the different systems. Related to the

33


different laying months of the investigation, the interaction SYS*MON showed a decrease in

shell breaking strength and increase in egg weight from laying month 3 to 12 within each

housing system tested. These findings corresponded to results of previous studies on egg shell

quality where increased egg size was accompanied by inferior egg shell quality and reduced

egg shell breaking strength due to constant egg shell mass and decreased capability of layers

to absorb calcium in the course of the laying period (Cordts et al., 2001). Although a decrease

of shell strength was observed in the present study, shell quality traits such as shell thickness,

shell density and shell weight increased from laying month 3 to 12.

The significantly lower number of meat spots in eggs stemming from hens kept in the aviary

system agreed with findings of Leyendecker et al. (2001), who detected a significantly lower

number of meat spots in eggs stemming from Lohmann Tradition free range and aviary layers

compared to caged layers, whereas the number of blood spots did not differ between the

different housing systems. According to Campo and Garcia Gil (1998), increased exposure to

stress was related to an increased incidence of internal egg inclusions. Hens kept in the aviary

system might have had more possibilities to perform natural behavioral traits, thus

experiencing less stress exposure compared to layers kept in Aviplus and EV 625a-EU.

With relation to the percentage of dirty and cracked eggs, hens kept in EV 625a-EU had

produced higher numbers of downgraded eggs compared to layers housed in the aviary

system and Aviplus. A high number of dirty and cracked eggs due to mislaid eggs in dust

baths was found to be problematic in furnished cages as downgraded eggs contribute to a rise

in production costs (Appleby et al., 2002). An increased number of cracked eggs (Duncan et

al., 1992) and dirty eggs (Guesdon and Faure, 2004; Mallet et al., 2006) was associated with

the incorporation of perches. Duncan et al. (1992) observed hens laying their eggs from

perches. In the current investigation, hens kept in the EV 625a-EU might have mislaid a high

number of eggs due to only 2 nest boxes per compartment, which did not provide enough

space for simultaneous use of all layers. Mallet et al. (2006) suggested that an improved

equipment of housing system would succeed in reducing the number of mislaid and therefore

dirty eggs if nest laying possibilities were enhanced. In the current study, elevated perches in

the EV 625a-EU might have provided the potential of laying eggs from perches, thus

increasing the number of cracked eggs. Also, eggs laid in nest boxes easily accumulated when

they rolled onto the egg belt due to the high number of hens per nest box. This might have

been primarily responsible for the high percentage of cracked eggs. Egg shell breaking

strength of eggs stemming from EV 625a-EU was not found to be responsible for the high

incidence of cracked eggs in the small group system as no differences in egg shell strength

34


could be detected between the three housing systems tested. An increased number of cracked

eggs in furnished cages was also described by Guesdon et al. (2006). In contrast, egg quality

in furnished cages and small group systems measured by Vits et al. (2005) met the high

qualitative standards related to conventional cages. Findings on significantly higher egg

production in the aviary system compared to EV 625a-EU and Aviplus have to be interpreted

carefully as high egg production can easily be spoiled by a large amount of downgraded eggs.

Daily egg mass did not differ among the three different housing systems tested, but the

number of dirty and cracked eggs detected in the aviary system significantly reduced the daily

salable egg mass compared to Aviplus. Due to the high incidence of downgraded eggs in EV

625a-EU, the small group system yielded the lowest daily salable egg mass per hen housed

compared to the other two housing systems.

The results of the present investigation showed that the elevated perches and enlarged group

sizes of the small group housing system did not provide enough stimuli to ameliorate humerus

bone strength of layers compared to furnished cages. However, a positive impact on tibia

bone strength of the ST perch variant was detected. Furthermore, hens in the small group

system had exhibited superior tibia bone strength at the end of the laying period compared to

Aviplus. At all times of the investigation, the aviary system was found to have a decisive

impact on humerus and tibia bone strength. Although tibia bone strength and keel bone

condition were positively correlated, an unfavorable keel bone status of layers kept in the

aviary system could not be prevented. In addition, perches in the BE position of EV 625a-EU

were found to have a negative impact on keel bone status compared to Aviplus, which was

primarily related to extended perching activities.

Egg shell quality parameters, except the percentage of cracked and dirty eggs, did not differ

between the 3 different housing systems tested. Although the small group system yielded

highest egg and yolk weights together with a sound egg production rate, the high number of

cracked and dirty eggs spoiled results on egg quality and resulted in the lowest daily salable

egg mass among the different housing systems tested.

ACKNOWLEDGEMENTS

The authors would like to thank Big Dutchman GmbH, Lohmann Tierzucht GmbH and

Deutsche Frühstücksei GmbH for financial support of this scientific project.

35


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39


TABLE 1. Analysis of variance for the traits humerus and tibia bone strength, keel bone

status, egg quality traits and egg production, daily egg mass and daily salable egg mass per

hen present

SYS GR(SYS) MON SYS*MON PP(SYS) Trait F-

value P F-

valueP F-

valueP F-

valueP F-

value P

Humerus strength (N) 255.2 *** 3.5 * 0.9 NS 2.3 * 0.2 NS Tibia strength (N) 82.0 *** 4.8 ** 1.2 NS 0.7 NS 2.0 NS Keel bone status (1-4) 17.5 *** 1.0 NS 1.8 NS 0.9 NS 1.4 NS Shell strength (N) 0.1 NS 0.3 NS 63.9 *** 1.7 * 0.6 NS Shell thickness (µm) 0.1 NS 0.7 NS 3.2 *** 2.6 *** 0.01 NS Shell density (mg/cm3) 0.4 NS 0.6 NS 17.1 *** 4.6 *** 0.01 NS Shell weight (g) 0.6 NS 0.9 NS 65.5 *** 4.6 *** 0.01 NS Haugh units 1.0 NS 0.8 NS 173.7 *** 5.1 *** 2.1 NS Blood spots (1-2) 6.4 ** 2.6 * 1.3 NS 1.1 NS 0.1 NS Meat spots (1-2) 9.2 *** 0.8 NS 0.9 NS 1.7 * 0.3 NS Albumen height (mm) 0.4 NS 0.5 NS 165.7 *** 5.0 *** 1.5 NS Yolk weight (g) 32.2 *** 2.0 NS 358.3 *** 3.7 *** 0.01 NS Yolk color (1-15) 0.2 NS 0.9 NS 16.7 *** 2.4 *** 2.1 NS Egg weight (g) 10.8 *** 5.4 *** 111.8 *** 2.8 *** 0.4 NS Dirty eggs (%) 11.7 *** - - - - - - - - Cracked eggs (%) 1.9 NS - - - - - - - - Egg production (%) 1.9 NS - - - - - - - - Egg mass (g) 0.9 NS - - - - - - - - Salable egg mass (g) 2.5 NS - - - - - - - - SYS: housing system; GR(SYS): group size within housing system; MON: laying month;

SYS*MON: interaction between housing system and laying month; PP(SYS): perch position

variant; * P ≤ 0.05, ** P ≤ 0.01, *** P ≤ 0.001.

40


TABLE 2. LS-means (LSM), their standard errors (SE) and significant differences between

housing systems for humerus and tibia bone strength, keel bone status, egg quality traits and

egg production, daily egg mass and daily salable egg mass per hen present

Aviplus (I) EV 625a-EU (II) Aviary system (III) Trait LSM SE LSM SE LSM SE

Humerus strength (N) 166.6B 4.2 167.5B 4.4 284.2A 4.1 Tibia strength (N) 120.9B 2.3 126.5B 2.4 159.0A 2.2 Keel bone status (1-4) 3.66B 0.1 3.52B 0.1 3.21A 0.1 Shell strength (N) 43.0a 0.8 42.9a 0.4 42.5a 1.0 Shell thickness (µm) 343.7a 1.9 343.6a 1.0 344.7a 2.3 Shell density (mg/cm3) 86.1a 0.6 85.5a 0.3 85.5a 0.8 Shell weight (g) 6.2a <0.1 6.2a <0.1 6.2a 0.1 Haugh units 81.7a 0.4 81.9a 0.2 82.6a 0.5 Blood spots (1-2) 0.13A <0.01 0.14A <0.01 0.09B <0.01 Meat spots (1-2) 0.86A <0.1 0.89A <0.1 0.81B <0.1 Albumen height (mm) 6.9a 0.1 7.0a <0.1 7.0a 0.1 Yolk weight (g) 17.1B <0.1 17.3A <0.1 16.8C 0.1 Yolk color (1-15) 12.7a 0.1 12.7a <0.1 12.6a 0.1 Egg weight (g) 61.0B 0.1 61.3B 0.1 60.4A 0.1 Dirty eggs (%) 1.62B <0.01 2.04A <0.01 1.99A <0.01 Cracked eggs (%) 1.32Bb <0.01 3.50A <0.01 1.52Cc <0.01 Egg production (%) 86.0B <0.01 86.2B <0.01 88.8A <0.01 Egg mass (g) 51.9a <0.01 51.7a <0.01 51.4a <0.01 Salable egg mass (g) 50.4Aa <0.01 48.8B <0.01 49.7Cc <0.01 EV: Eurovent; means within a row lacking a common superscript differ (P ≤ 0.05).

41


TABLE 3. LS-Means (LSM), their standard errors (SE) and significant differences of bone

breaking strength (N) and keel bone status between the two variants of perch positions in EV

625a-EU (EV) and Aviplus

EV ST (I) EV BE (II) Aviplus (III) Trait LSM SE LSM SE LSM SE

Humerus strength (N) 165.7a 6.0 169.3a 6.2 166.6a 4.2 Tibia strength (N) 129.6a 3.2 123.4ab 3.3 120.9b 2.3 Keel bone status (1-4) 3.58ab 0.08 3.46b 0.08 3.66a 0.1 Shell breaking strength (N) 43.2a 0.5 42.6a 0.5 43.0a 0.8 Shell thickness (µm) 343.6a 1.4 343.7a 1.4 343.7a 1.9 Shell density (mg/cm3) 85.6a 0.4 85.5a 0.4 86.1a 0.6 Shell weight (g) 6.2a 0.03 6.2a 0.03 6.2a 0.05 Haugh units 81.6a 0.4 82.3a 0.4 81.7a 0.4 Blood spots (1-2) 0.13a 0.01 0.14a 0.01 0.10a 0.01 Meat spots (1-2) 0.89a 0.02 0.88a 0.02 0.86a 0.01 Albumen height (mm) 6.9a 0.1 7.0a 0.1 6.9a 0.1 Yolk weight (g) 17.3A 0.1 17.3A 0.1 17.1B 0.1 Yolk color (1-15) 12.6a 0.04 12.7a 0.04 12.7a 0.06 Egg weight (g) 61.2a 0.2 61.4a 0.2 61.0a 0.1 ST: perches in stepped position, BE: back perch elevated; means within a row lacking a

common superscript differ (P ≤ 0.05).

42



group sizes within housing system for humerus and tibia bone strength, keel bone status and

selected egg quality traits

Aviplus P EV 625a-EU P Trait 10 (I) 20 (II) 30 (III) I-II I-III II-III 40 (I) 60 (II) I-II

Humerus strength (N)

170.8 ± 7.2

175.1 ± 7.2

154.0 ± 7.2

NS NS * 177.2 ± 6.2

157.8 ± 6.0

*

Tibia strength (N)

126.2 ± 3.9

126.7 ± 3.9

109.9 ± 3.9

NS ** ** 129.6 ± 3.3

123.3 ± 3.2

NS

Keel bone status (1-4)

3.64 ± 0.09

3.78 ± 0.09

3.56 ± 0.10

NS NS NS 3.54 ± 0.08

3.50 ± 0.08

NS

Blood spots (1-2)

0.11 ± 0.02

0.17 ± 0.02

0.11 ± 0.02

* NS * 0.14 ± 0.01

0.14 ± 0.01

NS

Egg weight (g) 61.2 ± 0.2

61.5 ± 0.2

60.4 ± 0.2

NS * *** 61.1 ± 0.2

61.5 ± 0.2

NS

EV: Eurovent, * P ≤ 0.05, ** P ≤ 0.01, *** P ≤ 0.001.

43



housing systems and laying months for humerus and tibia bone strength and keel bone status

Aviplus (I) EV 625a-EU (II) Aviary system (III) Laying Months LSM SE LSM SE LSM SE Humerus strength (N) 3 174.6B 8.8 167.5B 9.8 311.7A 8.2 6 165.9B 8.2 176.0B 9.1 298.1A 8.2 9 160.8B 8.4 159.9B 9.0 270.2A 8.2 12 165.2B 8.4 166.7B 7.5 256.7A 8.2 Tibia strength (N) 3 120.4B 4.8 121.2B 5.3 155.8A 4.4 6 123.7B 4.4 123.6B 4.9 159.6A 4.4 9 115.6B 4.5 121.7B 4.7 151.9A 4.4 12 124.1C 4.6 139.4B 4.0 168.8A 4.4 Keel bone status (1-4) 3 3.84a 0.12 3.78ab 0.13 3.49b 0.11 6 3.83A 0.11 3.66AB 0.12 3.42B 0.11 9 3.55A 0.11 3.22b 0.11 2.81C 0.11 12 3.41ab 0.11 3.43a 0.10 3.11b 0.11 EV: Eurovent; means within a row lacking a common superscript differ (P ≤ 0.05).

44


45

TABLE 6. Correlation coefficients (below the diagonal) and their error probabilities (above

the diagonal) between humerus and tibia bone breaking strength, keel bone status and body

weight of layers

Trait Bone strength Humerus

Bone strength tibia

Keel bone status Body weight of layers

Bone strength Humerus

- <0.001 0.154 <0.001

Bone strength tibia

0.408 - <0.001 <0.001

Keel bone status

0.069 0.271 - 0.770

Body weight of layers

0.182 0.368 0.014 -

Figure 1. Cross-section of the elevated perch

positions BE (back perch (BP) elevated) and ST

(stepped position with back and front perch (FP)

elevated) and of the central tube (CT) within

Eurovent 625a-EU compartments

Chapter IV

Bone strength and keel bone status of two layer strains kept in

furnished small group systems with different perch configurations

and group sizes


Chapter IV: Influence of different perch positions on bone strength and keel bone status

Bone strength and keel bone status of two layer strains kept in furnished

small group systems with different perch configurations and group sizes

B. SCHOLZ, S. RÖNCHEN, H. HAMANN and O. DISTL


Foundation, Hannover, Germany1

Abstract 1. The objective of the present study was to investigate whether an arrangement of

perches at two different heights within individual compartments of small group housing

systems (back perch elevated (BE), front perch elevated (FE) or both perches heightened

(ST)) combined with an enlarged group size would increase humerus and tibia bone breaking

strength and impact keel bone status.

2. Bone strength and keel bone status of two layer strains (Lohmann Selected Leghorn (LSL),

Lohmann Brown (LB)) kept in small group systems (SG 40-60 (groups of 40 and 60 hens),

SG 20-30 (20 and 30 hens)) with different perch configurations and furnished cages (FC, 10

and 20 hens, perches on an even height) were compared in two experimental trials under

identical management conditions.

3. Investigations were carried out at the end of the 6th and 12th laying month, comprising a

total of 576 hens. Layers were caged during rearing and transferred to the three housing

systems at the age of 18 weeks.

4. When all compartments of SG 40-60 had been incorporated with perches at two different

heights, humerus and tibia bone breaking strength in LSL layers significantly increased

compared to FC, whereas keel bone status was negatively impacted.

5. Within SG 40-60, the perch configurations BE and FE significantly increased humerus

bone strength of LSL layers compared to the ST perch position.

6. LB layers showed significantly higher bone strength in pens of 20 hens compared to

compartments of 30 hens in SG 20-30, whereas no effect of group size was detected for LSL

layers within the three housing systems tested.

7. Keeping hens in SG 40-60 with modified perch configurations was associated with

increased bone breaking strength of layers but brought about the problem of inferior keel bone

1Correspondence to: Professor O. Distl, Institute for Animal Breeding and Genetics, University of Veterinary Medicine Hannover (Foundation), Bünteweg 17p, 30559 Hannover, Germany, Phone: +49-511-9538875, Fax: +49-511-9538582. E-mail: [email protected]

48


status, presumably due to a high compression load on the keel during perching activities and

accidental perch collisions with keel bone.

INTRODUCTION The national implementation of the EU Council directive 1999/74/EC (19 July 1999) on

laying down minimum standards for the protection of laying hens has induced major changes

in laying hen husbandry. The German government has put a ban on furnished cages and

intends to replace these systems either by alternative housing systems or furnished small

group systems which have only recently been approved of as adequate substitutes. In

Germany, conventional cages will be entirely abandoned by the end of 2008. In

correspondence to the legal regulations, most EU countries will stick to conventional cages

until the end of 2011 and then replace them by the use of furnished cages. In several studies,

developments on conventional cages towards furnished house keeping systems have led to

positive achievements in bone breaking strength (Hughes and Appleby, 1989; Abrahamsson

and Tauson, 1993). So far, only very few data exists on furnished small group systems which

are further advancements of furnished cages. Furnished small group systems are designed to

keep group sizes of up to 60 laying hens per compartment and offer increased possibilities to

move due to a larger floor space. In correspondence to furnished cages, small group housing

systems are also equipped with perches, nest box, pecking and scratching area and devices to

shorten claws and provide a cage surface area of 750cm² per hen. Vits et al. (2005) analysed

humerus and tibia bone strengths of LSL layers kept in furnished cages and furnished small

group systems and found tibia bone strengths being comparable to bone strengths of hens kept

in an aviary system measured by Leyendecker et al. (2005). Due to the different designs of

the studies a fully matching comparison can only be carefully drawn. In an investigation by

Weitzenbürger et al. (2006), approximately 33% of layers kept in furnished cages and small

group housing systems experienced keel bone deformities throughout the laying period. These

alterations were supposed to be due to mechanical pressure on the keel bone, which occurred

during perching activities and was primarily influenced by general bone breaking strength.

Currently, furnished small group systems with modified perch configurations, which will be

implemented with the beginning of 2012, reflect the most advanced developments in laying

hen husbandry in Germany. In addition to furnished small group systems, these housing

systems are equipped with perches which are installed at two different heights within each

individual compartment. The modified perch positions aim to increase bone strength by

stimulating movements of layers, thus trying to minimise the problem of inactivity

49


osteoporosis. Small group systems and particularly small group systems with modified perch

positions were designed to meet the requirements of improved animal welfare and high

hygienic standards that are related to systems which are well protected from outside

environmental influences. In the course of developing such a laying hen husbandry system we

analysed bone breaking strength and keel bone status of Lohmann Selected Leghorn (LSL)

and Lohmann Brown (LB) layers kept in three different housing systems. For the first time

the effect of modified small group systems on bone strength and keel bone status was

measured and directly compared to furnished cages and furnished small group systems under

identical management conditions. Particular emphasis will be put on the influence of different

kinds of perch modifications within individual compartments and the influence of enlarged

group sizes.

MATERIALS AND METHODS Housing systems, trials and layer lines

The three housing systems tested (all provided by Big Dutchman, Vechta, Germany) were

located in parallel position to each other within the same experimental building (Farm

Wesselkamp, Ankum). All housing systems tested were built over four tiers and fully met the

EU legislative standards on keeping laying hens. The furnished cage system Aviplus (FC) and

the small group system (SG) Eurovent 625A-EU (SG 20-30) consisted of a block of double-

sided cages with solid side and solid (FC) rear partitions. Group sizes in FC comprised 10 and

20 layers (cage floor 1206 x 625 mm and 2412 x 625 mm respectively). In SG 20-30 pens of

20 and 30 hens were kept (2412 x 625 mm and 3618 x 625 mm). The small group system

Eurovent 625a-EU (SG 40-60) was built without a centre partition and accommodated group

sizes of 40 and 60 laying hens per compartment (2412 x 1250 mm and 3618 x 1250 mm).

Although group sizes differed, compartment height (450 - 525 mm) and space per hen (750

cm²) was identical for all compartments within the three housing systems tested. Two

experimental trials were investigated which comprised the period August 2004 to October

2006. In the first trial, approx. 4,500 Lohmann Selected Leghorn (LSL) and 4,500 Lohmann

Brown (LB) layers were kept, which were evenly distributed over the three systems. In SG

20-30 and SG 40-60, each tier of the housing systems tested contained three to four

successive compartments of LSL and LB hens, which were arranged in alternate order. In FC,

nine successive compartments of LSL and LB hens alternated. In the second trial, only LSL

hens were used (approx. 9,000). All laying hens included in the investigation were cage-

reared and transferred to the three housing systems at the age of 18 weeks.

50


Perch positions and perch design

Compartments of both the SG 20-30 and FC were equipped with a front and back perch. Four

perches per compartment were installed in the SG 40-60 respectively. Perches were

incorporated in parallel position to the length of each compartment, allowing each hen 150

mm perch of its disposal. With reference to perch positions, a certain number of

compartments of SG 20-30 and SG 40-60 were modified according to the legal demands on

the modified small group system in each trial. One of the major requirements is the

incorporation of perches at two different heights within each compartment. Perch positions in

the systems tested comprised perches installed on an even level (NE, not elevated, 90 mm

distance to cage floor), the front perch being elevated (FE, 200 mm distance to cage floor), the

back perch being heightened (BE, 200 mm distance to cage floor) or both perches being

elevated and incorporated in a stepped position (ST, 200 and 275 mm distance to cage floor)

(Figure 1). In SG 20-30 compartments, the perch modifications NE, BE and FE were tested.

In SG 40-60 compartments the effect of all four types of perch modifications was analysed

(Table 1). In addition to the other two housing systems, the central tube for the automatic

distribution of the dust bathing substrate in SG 40-60 served as additional perching space.

Perches in FC were installed on an even level in both trials. All perches were made out of

white, polished plastics (RAL9010, PVC, rigid) and had a thickness of 30 mm. They were

oval shaped with a flattened top and underside. The contact area for the layers’ feet was 20.1

mm. Front and back parts of the perch were formed in a convex shape. Perches in SG 40-60,

which were modified in their position were roundly shaped and their surface was made out of

abraded, galvanised zinc.

Management, feeding and laying performance

During both trials laying hens were subjected to identical management conditions.

Throughout the rearing period, hens received a prophylactic treatment according to a

commonly accepted vaccination scheme for laying hens. In addition, layers were vaccinated

against coccidiosis, E. coli, pox and pneumovirus infection. During the laying period, hens

were vaccinated against Newcastle disease and infectious bronchitis in regular intervals. An

identical lighting scheme was employed for all three housing systems tested. The lighting

period was gradually stepped up to 14 h per day. Hens were given a standard diet for laying

hens which was distributed three to four times per day per automatic food chain. An analysis

of food components was conducted in regular intervals, thus monitoring and ensuring the

nutritional value of the diet fed. Water was supplied ad libitum per nipple drinkers. The

incorporated pecking and scratching area (610 x 210 mm in FC, 600 x 260 mm in SG 20-30

51


and SG 40-60) was automatically supplied with a dust bathing substrate once a day. In SG 20-

30 and SG 40-60, two pecking and scratching areas were incorporated within each

compartment and arranged at opposite sides of the next boxes. In FC, one pecking and

scratching area was located right beside the nest box and a metal gate limited the access to

11am until 3pm. Production performance per housing system was recorded on a daily basis.

Analysis of bone breaking strength

At the end of the 6th and 12th laying month of both experimental trials 48 hens were

randomly chosen from each housing system, considering layer strain (first trial) and group

size within each housing system to equal numbers (576 hens in total). Before slaughter, body

weight of hens was recorded. Alternately the left or right humerus and tibia bones were

removed from muscles and tendons, dissected and stored for one day (+ 4°C) until bone

strength analysis. Bone breaking strength was measured by using a three-point-bending

machine (“Zwick/Z2,5/TNIS”, Zwick-Roell, Ulm, Germany). Bone ends were placed on two

supports (humerus: 40 mm, tibia: 90 mm distance) and a constant, perpendicular force was

applied until bone fracture. Bone strength was automatically recorded and measured in

Newton (N).

Evaluation of keel bone status

Reporting of keel bone status was carried out following the dissection of humerus and tibia

bones. After removal of the skin, keel bones of layers were evaluated visually and per

palpation. According to the severity of deviations (s-shaped deformities, osteal proliferations

and dorso-ventral compressions), keel bone status was recorded on a scale from 1 to 4 (1 =

severe deformity, 2 = moderate deformity, 3 = slight deformity, 4 = no deformity).

Statistical analysis

Statistical analysis was carried out using Residual Maximum Likelihood (REML) with the

MIXED procedure of SAS, version 9.1.3. (Statistical Analysis System Institute Inc., Cary,

NC, USA, 2006). For the first trial, housing system, layer line, group size within housing

system, laying month and perch position (PP) within housing system and layer line were

employed as fixed effects. The effect of PP was also tested within housing system, layer line

and group size and did not have a significant effect. The interactions between layer line and

housing system and layer line and group size within housing system were also included in the

model. The individual compartments (comp) within housing system, layer line and group

52


sizes were treated as a randomly distributed effect. Body weight (bw) of the layers within

layer line was a linear covariate. Each laying trial was analysed separately. The model was

reduced by the fixed effect layer line (LIN) and its interactions for statistical analysis of the

second trial.

Yijklmnop = µ + SYSi + LINj + GR(SYS)ik + LIN*SYSij + LIN*GR(SYS)ijk + MONl +

PP(LIN*SYS)ijm + compn + b x bw(LIN)jo + eijklmnop

Yijklmnop humerus and tibia bone breaking strength/keel bone status (first trial)

μ model constant

SYSi fixed effect of housing system (i=1 to 3)

LINj fixed effect of layer line (j=1 to 2)

GR(SYS)ik fixed effect of group size within housing system (k=1 to 5)

LIN*SYSij fixed effect of the interaction between layer line and housing system

(ij=1 to 6)

LIN*GR(SYS)ijk fixed effect of the interaction between layer line and group size within

housing system (ijk=1 to 12)

MONl fixed effect of laying month (l=1 to 2)

PP(SYS*LIN)ijm perch positions within housing system and layer line (ijm=1 to 12)

compn randomly distributed effect of individual compartments within housing

systems (n=1 to 91)


bw(LIN)jo body weight of layers within layer line

eijklmnop random error variation

Results of variance analysis were regarded significant when the error probability was less

than 5% (p< 0.05). Statistical analysis was also carried out by excluding data of the furnished

cage system Aviplus from the model and furthermore, by entirely excluding the fixed effect

SYS and statistically evaluating the effect of perch positions within each EV system

separately. The results did not differ from the statistical model described above.

53


RESULTS For both trial periods, the overall probability levels of the effects SYS, PP(SYS*LIN) and

GR(SYS) for humerus and tibia bone strength and keel bone status are given in Table 2. The

least square means (LSM), standard errors (SE) and error probabilities of analysis of variance

for bone breaking strength and keel bone status by housing system and layer line are

presented in table 3. In the first trial, no significant difference in humerus and tibia bone

strength could be detected between the three different housing systems tested although

humerus and tibia bone strength of both layer lines measured in the SG systems tended to be

higher compared to FC. In the second trial, when all perch positions within compartments of

SG 40-60 had been modified according to the demands on the modified small group system,

tibia and humerus bone strengths of LSL layers were found to be significantly higher in

comparison to FC. The tendency of a higher bone breaking strength of hens kept in SG 20-30

in the first trial compared to FC was confirmed in the second trial. LSL layers in SG 20-30

had a significantly higher humerus and tibia bone strength compared to FC although the

percentage of compartments with perch modifications had not differed in SG 20-30 between

the two trials. In correspondence to the first trial, no significant difference between humerus

and tibia bone strength was found between the two SG systems in the second trial. Keel bone

status did not differ significantly between housing systems in the first trial. In the second trial,

keel bone status of layers kept in SG 40-60 (all perches in modified positions) was scored

almost significantly lower than hens kept in the SG 20-30 (p = 0.058).

With reference to perch position varieties in SG 40-60, no significant difference in bone

breaking strength could be detected between the variants NE and BE for both layer lines in

the first trial. Although the overall probability level for the effect PP (SYS*LIN) was still not

significant for humerus bone strength (p = 0.14) in the second trial, hens kept in

compartments with the BE and FE positions had significantly higher humerus bone breaking

strength compared to layers housed in compartments with perches in the ST position, whereas

no significant influence of perch positions on tibia bone strength was found (Table 4). Keel

bone status did not differ between the different perch modifications in both trials. Results of

variance analysis for perch varieties of hens kept in SG 20-30 are illustrated in table 5. In the

first trial, no significant difference could be detected between the three kinds of perch

modifications except for tibia bone strength of LSL layers. Tibia bone strength was found

significantly higher in the NE position compared to FE. This finding could not be repeated in

the second trial as hens kept in compartments with FE modification showed significantly

higher tibia bone strength in comparison to layers kept in NE compartments. In

54


correspondence to SG 40-60, keel bone status did not differ between the different perch

positions within SG 20-30. The effect of group size within housing system did not prove a

significant influence on LSL bone strength, whereas LB layers produced a significantly

higher humerus and tibia bone strength in compartments of 20 hens compared to pens of 30

layers in SG 20-30 (Table 6). No effect of group size on keel bone status could be detected.

Residual correlations between humerus and tibia bone strength, keel bone status and body

weight of hens showed a significant positive residual correlation between humerus and tibia

bone breaking strength and between these two traits and keel bone status, whereas residuals of

body weight did not significantly correlate with residuals of the traits bone strength and keel

bone status.

In the first trial period, layers showed a laying performance (% hen day) of 88.7 in SG 40-60

and 88.4 in SG 20-30 and FC. In the second experimental trial, egg production rate was 89.2

(SG 40-60), 90.5 (SG 20-30) and 88.8 (FC). All standard errors related to the egg production

rates given were 0.002.

DISCUSSION Several investigations on laying hen bone strength have clearly stated that osteoporosis in

layers is due to lack of physical movement resulting from environmental constraints of the

housing system and its equipment (Baxter, 1994; Webster, 2004) together with a switch from

structural to medullary bone, which occurs when a hen reaches sexual maturity (Whitehead

and Fleming, 2000). The incorporation of perches on an even level had proved being

successful in increasing bone strength in a variety of studies compared to conventional cages

(Barnett et al., 1997; Leyendecker et al., 2002). In the first experimental trial hens kept in the

SG systems reflected a tendency of increased bone strength within layer line compared to the

FC system. This result might have been less distinct for LSL layers compared to findings of

the second trial, as the number of hens per observation was reduced due to the two layer

strains used in trial one. In addition, less compartments of SG 40-60 were equipped with

perch modifications in the first trial. In the second experimental trial, humerus and tibia bone

strengths of LSL layers kept in SG 40-60 with all perches being installed at two different

heights were found to be significantly higher compared to hens kept in FC. Elevated perches

together with an enlarged floor space in SG 40-60 seemed to have served as a strong stimulus

to movement. In a study by Olsson and Keeling (2000) layers kept in litter pens preferred

perches at heights of 63 cm compared to lower perches and showed a very high acceptance.

Abrahamsson et al. (1996) found increased humerus bone strength of layers kept in get-away

55


cages with perches at different levels, thus proving a positive effect of perch arrangements at

different heights. Vits et al. (2005) analysed bone strength of LSL and LB layers kept in a

furnished small group system (Eurovent 625a-EU) with perches incorporated on an even

level. The results of humerus bone strength of LSL layers kept in SG 40-60 in the second trial

(191.7 N) clearly exceeded bone strength measured by Vits et al. (2005). The authors reported

humerus bone strength of 185.3 N pooled for both layer lines and found LB hens having

stronger humerus bones than LSL layers. Tibia bone strength between these two

investigations hardly differed. In SG 40-60, humerus bone strength of LSL layers kept in

compartments with BE and FE perch positions was significantly higher compared to the ST

position. Duncan et al. (1992) analysed the effect of perch arrangement and design on tibia

bone strength. The authors discovered that hens more frequently used perches of rectangular

cross-section compared to round ones and indicated that hens were more unstable on circular

perches. Perches incorporated in the ST position were roundly shaped. This might have

reduced the stimulus to agitation due to less perch acceptance. The colour of perches in the

ST position (dark grey) compared to only the elevated perch being of dark grey colour in the

FE and BE position might have also influenced perching activities. Taylor et al. (2003)

detected hens’ movements between perches in non-cage systems be inhibited when perches

were of dark colour compared to white coloured perches. They suggested altering perch

colours in order to make perches more visible and to provide a better approach. Lower

humerus bone strength of layers kept in compartments with the ST position might have also

been due to less effect of exercise resulting from a closer vertical distance between back and

front perch perches (75 mm) in comparison to the BE and FE modifications (110 mm vertical

distance). Tibia bone strength was not affected by different modifications of perch

arrangements in SG 40-60. Hens kept in SG 20-30 showed very inconsistent reactions

towards the different perch positions regarding tibia bone strength. The effect of the two

variants NE and FE in the first trial was completely reversed in the second trial. This result is

difficult to explain. Some authors found both humerus and tibia bone strength be positively

affected by different cage designs or housing systems (Knowles and Broom, 1990;

Leyendecker et al., 2001), whereas others could not state any effects on tibia bone strength

(Hughes and Wilson, 1993; Abrahamsson and Tauson, 1997; Moinard et al., 1998). In this

context, tibia bone strength does not seem a very reliable indicator of responding to

modifications in cage equipment. Effects on tibia bone strength can be rather diverse. A study

by Fleming et al. (1994) pointed out that humerus is the bone which shows the largest

responses to different husbandry systems. Therefore, effects on tibia bone strength should be

56


interpreted rather carefully and might not easily be reproduced, as the results of trial one and

two have clearly shown. Differences in group sizes did not produce significant effects on LSL

bone strength in both trials. This result corresponds to findings of Vits et al. (2005). In their

investigation, no differences related to bone breaking strength could be detected between

layers housed in small group pens with varying group sizes. In the current study, LB layers

kept in SG 20-30 reflected significantly higher humerus and tibia bone strength in

compartments of 20 layers compared to pens of 30 hens. The smaller floor space of hens kept

in compartments of 20 hens having a positive influence on bone strength of LB layers is

difficult to explain. Perch arrangement and space per hen (750 cm² per hen) was identical for

both group sizes. As group sizes of 30 hens can reflect a high degree of social disruption

(Keeling et al., 2003), LB hens in the smaller compartments (20 hens) might have been less

displaced when stepping up on elevated perches and exhibiting perching activities. In

addition, the performance of more weight bearing exercise for a longer time when using

elevated perches without disturbance could have contributed to an increase in bone strength.

The equipment of housing systems does not only influence bone strength but also has an

impact on keel bone, which is very vulnerable due to its exposed anatomical location. Keel

bone status was found to be negatively associated with house keeping systems which are

equipped with perches (Appleby et al., 1993; Abrahamsson et al., 1996). Findings in previous

studies have suggested that hens kept in aviary housing systems are predisposed to suffer

from keel bone deviations due to accidental flight and landing collisions with perches

(Gregory et al., 1991). Considering data on keel bone status of a European study (Elson and

Croxall, 2006), conventional and furnished cages were found to be more favourable housing

systems compared to aviaries. In comparison to the first trial, when 33 % of compartments

were equipped with elevated perch variants in SG 40-60, all compartments were incorporated

with perches in modified configurations in the second trial and hens experienced an almost

significantly lower keel bone status compared to hens kept in SG 20-30. The provision of

perches at two different heights in SG 40-60 seemed to have had a negative impact on the

keel. The results of increased bone strength in SG 40-60 compared to FC suggested a high

acceptance of perches in the former system. Long-term perching activities have been

described to produce keel bone deviations due to inadequate mechanical pressure on the keel

(Wahlström et al., 2001). Elevated perches in SG 40-60 were roundly shaped, which might

have led to increased local pressure on keel bone while perching. Tauson and Abrahamsson

(1994) found the incidence of keel bone lesions clearly affected by perches with a round

design. An inadequate arrangement of perches has also been described to cause keel bone

57


deviations. Scott et al. (1997) suggested a minimised horizontal and vertical distance of

perches at different heights in order to support hens moving downwards without failures. In

the current study the maximal vertical distance between perch and cage floor was 275 mm

(ST), which should not have born a risk of injury while accessing perches. Moinard et al.

(2004) suggested perch distances not to exceed 600 mm in extensive housing systems in order

to avoid injuries through missing perches. The horizontal distance of perches was

approximately 150 mm, which should have provided hens an easy move between perches.

Inferior keel bone status of layers kept in SG 40-60 might therefore primarily be due to

extended perching pressure on keel bone. Also, disruptive reactions in the stocking

environment provided (750 cm² space per hen) together with a great proportion of dark

coloured perches might have contributed to accidental collisions of keel bone with perches.

As regards the perch arrangement, hens should have very well been able to negotiate the

distances provided in SG 40-60 properly. Keel bone status was not influenced by group size,

which is in agreement with findings of VITS et al. (2005). In the present study, bone strength

and keel bone status were positively correlated which corresponds to a study by Bishop et al.

(2000). Also in agreement with Bishop et al. (2000), strength of tibia showed higher

correlations with keel bone status than strength of humerus. As bone strength characteristics

respond rapidly to environmental changes allowing more freely moving of layers,

improvements in housing systems in this respect should increase the strength of the whole

skeleton.

The results of the current study showed that the incorporation of perches at different heights

in the SG systems positively impacted bone strength of humerus and tibia. In SG 40-60, the

variants FE and BE were found to be favourable perch positions compared to the ST

configuration with relation to humerus bone strength. The influence of group size was found

to be less distinct. Although the study demonstrated positive correlations between humerus

and tibia bone strength and keel bone status, keel bone in SG 40-60 with modified perches did

not improve as much that it could withstand extended pressure from perching activities and

possible perch collisions.

ACKNOWLEDGEMENTS The authors would like to thank Big Dutchman GmbH, Lohmann Tierzucht GmbH and


58


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ELSON, H.A. & CROXALL, R. (2006) European study on the comparative welfare of laying

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structure and breaking strength in laying hens housed in different husbandry systems.

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HUGHES, B.O. & WILSON, S. (1993) Comparison of bone volume and strength as measures of

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KEELING, L.J., ESTEVEZ, I., NEWBERRY, R.C. & CORREIA, M.G. (2003) Production-related

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LEYENDECKER, M., HAMANN, H., HARTUNG, J., KAMPHUES, J., RING, C., GLÜNDER, G.,

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DISTL, O. (2005) Keeping laying hens in furnished cages and an aviary housing system

enhances their bone stability. British Poultry Science, 46: 536-544.

MOINARD, C., MORISSE, J.P. & FAURE, J.M. (1998) Effect of cage area, cage height and

perches on feather condition, bone breakage and mortality of laying hens. British Poultry

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MOINARD, C., STATHAM, P. & GREEN, P.R. (2004) Control of landing flight by laying hens:

implications for the design of extensive housing systems. British Poultry Science, 45: 578-

584.

OLSSON, I.A. & KEELING, L.J. (2000) Night-time roosting in laying hens and the effect of

thwarting access to perches. Applied Animal Behaviour Science, 68: 243-256.

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NC, USA.

SCOTT, G.B., LAMBE, N.R. & HITCHCOCK, D. (1997) Ability of laying hens to negotiate

horizontal perches at different heights, separated by different angles. British Poultry

Science, 38: 48-54.

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TAUSON, R. & ABRAHAMSSON, P. (1994) Foot and skeletal disorders in laying hens. Acta

Agriculturae Scandinavica, 44: 110-119.

TAYLOR, P.E., SCOTT, G.B. & ROSE, S.P. (2003) Ability of laying hens to negotiate jumps

between horizontal perches: effects of light intensity and perch colour. British Poultry

Science, 44 (Supplement 1): 32-33.

VITS, A., WEITZENBÜRGER, D., HAMANN, H. & DISTL, O. (2005) Production, egg quality,

bone strength, claw length and keel bone deformities of laying hens housed in furnished

cages with different group sizes. Poultry Science, 84: 1511-1519.

WAHLSTRÖM, A., TAUSON, R. & ELWINGER, K. (2001) Plumage condition and health of

aviary-kept hens fed mash or crumbled pellets. Poultry Science, 80: 266-271.

WEBSTER, A.B. (2004) Welfare implications of avian osteoporosis. Poultry Science, 83: 184-

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WEITZENBÜRGER, D., VITS, A., HAMANN, H. & DISTL, O. (2006) Evaluation of small group

housing systems and furnished cages concerning keel bone deformities, plumage condition,

claw length and body weight in layer strains Lohmann Selected Leghorn and Lohmann

Brown. Archiv für Tierzucht, 49: 89-102.

WHITEHEAD, C.C. & FLEMING, R.H. (2000) Osteoporosis in cage layers. Poultry Science, 79:

1033-1041.

61


Figure 1. Perch positions of the small group system Eurovent 625a-EU (SG 40-60)

NE

4

3 2 1

1. central tube for supply of dust bathing substrate 2. back perch 3. front perch 4. nipple drinker

FE ST BE NE: perches not elevated; FE: front perch elevated; ST: perches in a stepped position; BE: back perch elevated; non-elevated perches were made out of white plastics; surfaces of elevated perches were made out of galvanised zinc. Table 1. Number of compartments, number of hens per treatment and percentage of perch positions tested by housing system FC SG 20-30 SG 40-60 Perch configuration NE NE BE FE NE BE - Trial 1 Number of compartments 36 20 4 8 16 7 - Number of hens per treatment 96 56 16 24 64 32 - Percentage of perch positions 100 58 17 25 67 33 - NE NE BE FE ST BE FE Trial 2 Number of compartments 36 14 4 6 8 8 8 Number of hens per treatment 96 56 16 24 32 32 32 Percentage of perch positions 100 58 17 25 33 33 33 NE: perches not elevated; FE: front perch elevated; ST: perches in a stepped position; BE: back perch elevated.

Table 2. Overall probability level (p) of the effects housing system (SYS), perch position within housing system and layer line (PP(SYS*LIN)) and group size (GR(SYS)) for humerus and tibia bone strength and keel bone status Humerus Tibia Keel bone Humerus Tibia Keel bone Trial 1 Trial 2 SYS 0.20 0.41 0.98

*** * 0.16

PP(SYS*LIN) 0.71 0.29 0.86 0.14 0.17 0.83 GR(SYS) 0.22 * 0.54 0.88 0.54 0.28 T1: Trial 1; T2: Trial 2; *: p ≤ 0.05; ***: p ≤ 0.001.

62


Table 3. LS-means (LSM), their standard errors (SE) and significant differences between housing systems for humerus and tibia bone strength [N] and keel bone status

FC (I) SG 20-30 (II) SG 40-60 (III) I-II I-III II-IIITrait LSM SE LSM SE LSM SE p p p

Trial 1 Humerus LSL 159.1 7.1 172.3 7.8 172.8 7.4 0.16 0.13 0.96 Humerus LB 226.7 7.1 235.7 7.6 230.1 6.7 0.34 0.71 0.57 Tibia LSL 136.5 4.4 141.5 4.8 140.2 4.6 0.39 0.51 0.84 Tibia LB 135.2 4.4 139.7 4.7 140.3 4.2 0.43 0.37 0.93 Keel bone LSL 3.39 0.1 3.47 0.1 3.44 0.1 0.59 0.71 0.86 Keel bone LB 3.59 0.1 3.47 0.1 3.52 0.1 0.42 0.62 0.76

Trial 2 Humerus LSL 171.0 3.6 183.7 4.2 191.7 3.6 * *** 0.15 Tibia LSL 137.6 2.4 147.1 2.8 145.6 2.4 * * 0.68 Keel bone LSL 3.55 0.1 3.66 0.1 3.48 0.1 0.22 0.47 0.058*: p ≤ 0.05; ***: p ≤ 0.001.

Table 4. LS-means (LSM), their standard errors (SE) and significant differences between perch positions of SG 40-60 for humerus and tibia bone strength [N] and keel bone status

BE (I) ST (II) FE (III) NE (IV) I-IV Trait LSM SE - - LSM SE p

Trial 1 Humerus LSL 168.0 11.2 - - 177.5 8.4 0.47 Humerus LB 220.1 10.7 - - 240.1 7.8 0.13 Tibia LSL 138.7 7.1 - - 141.8 5.2 0.71 Tibia LB 143.1 6.7 - - 137.5 4.9 0.50 Keel bone LSL 3.48 0.18 - - 3.41 0.14 0.74 Keel bone LB 3.51 0.17 - - 3.52 0.13 0.98

BE (I) ST (II) FE (III) I-II I-III II-IIITrait LSM SE LSM SE LSM SE p p p

Trial 2 Humerus LSL 199.4 6.3 178.4 6.3 197.3 6.3 * 0.81 * Tibia LSL 147.9 4.2 146.3 4.2 142.6 4.2 0.79 0.37 0.53 Keel bone LSL 3.40 0.1 3.51 0.1 3.54 0.1 0.67 0.81 0.82 BE: Back perch elevated; ST: stepped position; FE: front perch elevated; NE: perches not elevated; *: p ≤ 0.05.

63


64

Table 5. LS-means (LSM), their standard errors (SE) and significant differences between perch positions of SG 20-30 for humerus and tibia bone strength [N] and keel bone status

NE (I) BE (II) FE (III) I-II I-III II-IIITrait LSM SE LSM SE LSM SE p p p

Trial 1 Humerus LSL 179.0 8.9 167.8 15.5 170.0 2.6 0.52 0.54 0.91 Humerus LB 234.0 8.4 242.3 15.7 230.7 2.5 0.63 0.82 0.56 Tibia LSL 151.1 5.5 142.2 9.7 131.2 7.8 0.41 * 0.37 Tibia LB 134.8 5.2 136.5 9.8 147.8 7.8 0.87 0.16 0.36 Keel bone LSL 3.29 0.1 3.72 0.3 3.39 0.2 0.12 0.67 0.30 Keel bone LB 3.45 0.1 3.48 0.3 3.48 0.2 0.91 0.92 0.98

Trial 2 Humerus LSL 183.3 4.8 181.3 8.9 186.4 7.3 0.84 0.72 0.67 Tibia LSL 142.0 3.2 143.8 5.9 155.5 4.8 0.80 * 0.12 Keel bone LSL 3.70 0.1 3.59 0.2 3.70 0.1 0.51 0.98 0.55 NE: perches not elevated: BE: back perch elevated; FE: front perch elevated; *: p ≤ 0.05.

Table 6. LS-means (LSM), their standard errors (SE) and significant differences between group sizes within housing system for humerus and tibia bone strength [N] and keel bone status

FC SG 20-30 SG 40-60 Trait 10 20 p 20 30 p 40 60 p

Trial 1 Humerus LSL 158.7

± 9.5 159.4 ± 9.3

0.96 175.6 ± 10.3

169.0 ± 9.6

0.60 176.7 ± 9.6

168.8 ± 9.7

0.52

Humerus LB 219.6 ± 9.3

233.7 ± 9.5

0.26 248.5 ± 9.6

222.8 ± 10.1

* 220.5 ± 9.2

239.8 ± 9.0

0.12

Tibia LSL 142.1 ± 5.8

130.9 ± 5.8

0.14 145.7 ± 6.4

137.2 ± 6.0

0.28 139.4 ± 6.0

141.0 ± 6.1

0.84

Tibia LB 133.1 ± 5.7

137.3 ± 5.9

0.58 150.0 ± 6.0

129.4 ± 6.2

** 135.1 ± 5.7

145.5 ± 5.7

0.18

Keel bone LSL 3.3 ± 0.2

3.5 ± 0.2

0.39 3.3 ± 0.2

3.6 ± 0.2

0.19 3.4 ± 0.2

3.5 ± 0.2

0.67

Keel bone LB 3.6 ± 0.2

3.6 ± 0.2

0.97 3.5 ± 0.2

3.5 ± 0.2

0.99 3.4 ± 0.1

3.6 ± 0.1

0.37

Trial 2 Humerus LSL 171.1

± 4.9 171.0 ± 5.1

0.98 180.7 ± 5.5

186.6 ± 5.5

0.42 191.6 ± 5.1

191.8 ± 5.1

0.98

Tibia LSL 139.2 ± 3.4

136.0 ± 3.4

0.50 145.9 ± 3.7

148.2 ± 3.6

0.63 142.6 ± 3.4

148.5 ± 3.4

0.22

Keel bone LSL 3.5 ± 0.1

3.6 ± 0.1

0.32 3.6 ± 0.1

3.7 ± 0.1

0.16 3.4 ± 0.1

3.5 ± 0.1

0.34

*: p ≤ 0.05; **: p ≤ 0.01.

Chapter V

Effect of housing system, group size and perch position on H/L-

ratio in laying hens

B. Scholz, S. Rönchen, H. Hamann, H. Pendl and O. Distl

Archiv für Geflügelkunde

Chapter V: Stress perception in laying hens

H/L-ratio in laying hens

Effect of housing system, group size and perch position on H/L-ratio in laying hens

Einfluss von Haltungssystem, Gruppengröße und Sitzstangenposition auf den H/L-Ratio

bei Legehennen

BRITTA SCHOLZ1, SWAANTJE RÖNCHEN1, H. HAMANN1, HELENE PENDL2 and O. DISTL1

1 Institute of Animal Breeding and Genetics, University of Veterinary Medicine Hannover, Hannover, Germany

2 PendLab, Avian Diagnostic Microscopy, Steinhausen, Switzerland

66


Introduction

Due to the EU Council directive 1999/74/EC on laying down minimum standards for the

protection of laying hens, major changes in laying hen husbandry will occur in the near

future. Conventional cages will have to be replaced by furnished cages or small group

housing systems by the end of 2011 in all European countries. Furthermore, the German

government has banned the use of furnished cages after 2011 and has only recently approved

a small group housing system with elevated perch positions as an adequate substitute together

with other alternative housing systems. Compartments of the small group housing system are

equipped with perches at 2 different heights and provide space to house 40 or more hens.

These systems are supposed to combine increased animal welfare with high hygienic and

economic standards that are related to cage keeping systems. The level of stress which is

experienced by laying hens throughout the laying period is an important welfare criterion,

which not only affects layers’ health and resistance against diseases but also impacts

production performance (AL-MURRANY et al., 2006). A well recognized parameter to measure

the amount of stress imposed on layers is the heterophil to lymphocyte (H/L) ratio, which was

described by GROSS and SIEGEL (1983). An increased H/L ratio in response to stressors

reflects a reliable measure of the bird’s perception of environmental stress. Only very few

data exists on the effect of housing system or cage design on the H/L ratio in laying hens.

CAMPO et al. (2005) found a significant decrease of the H/L ratio in hens kept in cages

equipped with perches compared to those without. In a study by ELSTON et al. (2000) the cage

type preference (solid vs open cages) for layers was analysed and a decrease in the H/L ratio

in open cages, which were preferred by hens, was found. These findings provide evidence that

housing systems and particularly cage designs which meet layers’ needs can very well reduce

the level of chronic stress in hens. The purpose of the present investigation was to compare

the H/L ratio of laying hens kept under identical management and feeding conditions in 3

different housing systems (small group housing system with elevated perches, furnished

cages, aviary housing system) and for the first time to analyse the degree of stress imposed on

layers by the different housing environments in a direct comparison. Also, the effect of

different group sizes and perch positions on the H/L ratio of layers kept in small group

housing systems was tested. Perch positions and group sizes are strongly discussed

parameters in the current development of the small group housing system.

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Materials and Methods

Housing Systems

The 3 housing systems examined (provided by Big Dutchman, Vechta, Germany) were

established in parallel position to each other in 3 different rooms of the same experimental

building. The small group housing system Eurovent (EV) 625a-EU consisted of a three-tier

block of compartments without centre partitions. Pens were separated by solid side partitions

and comprised group sizes of 40 and 60 layers to equal shares. Compartments of EV were

evenly distributed over the 3 levels of the system. The floor space provided was 2,412 x 1,250

mm (40 hens) and 3,618 x 1,250 mm (60 hens) respectively. Four perches per compartment

were installed in parallel position to the length of each compartment, offering each laying hen

15 cm perching space. Perches were either installed with the back perches being elevated

(BE) or both front and back perches being heightened and incorporated in a stepped position

(ST). The central tube for the automatic distribution of dust bathing substrate served as

additional perching space. The furnished cage system Aviplus was implemented as a three-

tier block of double-sided cages with solid side and rear partitions. Compartments comprised

group sizes of 10 layers (bottom tier, 1,206 x 625 mm floor space), 20 layers (medium tier,

2,412 x 625 mm) and 30 layers (top tier, 3,618 x 625 mm). Each compartment contained 2

parallel perches, which were installed on an even level. EV and Aviplus system were

equipped with nest boxes, dust baths, devices to shorten claws and provided layers with a

cage surface area of 750 cm² per hen. The EU legislative standards on keeping laying hens

(EU directive 1999/74/EG) were fully met. The aviary housing system (model “Natura”) was

equipped with a three-tier central block within a fully littered indoor floor space. It was

divided into 2 compartments, which were located within the same room (floor space per pen:

3,650 x 15,980 mm). Each compartment contained 1,250 laying hens and had direct access to

a separate, covered outdoor area. The 2 separate outdoor areas contained litter and were

provided with occupational material (hay) once a day (floor space per outdoor area: 3,400 x

20,980 mm). The aviary system was equipped with family nest boxes, which were attached on

the walls opposite the central block. Nest boxes were connected via footboards with the

medium level of the system. Furthermore, perches were installed in front of the second and

above the top level.

Trial Period, Layer Strain and Management

The experimental trial investigated started in September 2005 and ended in September 2006.

A total number of 5,500 floor-reared Lohmann Silver laying hens was transferred to the

68


particular housing system at the age of 18 weeks. Hens were reared within the same flock,

thus ensuring fully identical rearing conditions. Hens were subjected to fully identical

management and feeding conditions. A commonly accepted immunisation scheme for laying

hens was employed throughout the rearing and laying period. Hens received a common two-

phase layer diet, which was automatically provided via food chains 3 to 4 times per day. Food

components were analyzed in regular intervals. The nutritional value averaged out at 10.9 MJ

ME, 16.5% crude protein, 3.89% calcium and 0.48% total phosphorus. Water was supplied ad

libitum from nipple drinkers. Hens in all 3 housing systems tested were given 14 hours of

artificial light per day (20 lux). The light scheme in the indoor part of the aviary system was

adapted to seasonal daylight fluctuations and the beginning of the light period varied from

5am (3rd laying month) up to 7.15am (12th laying month). Access to the outdoor areas was

only provided within the 14 hours light period. In the 8th laying month, 3 treatments against

the red mite (Dermanyssus gallinae) with Intermitox (Propoxur) were conducted in all 3

housing systems tested within a period of 13 days.

Evaluation of White Blood Cell Numbers and Heterophil to Lymphocyte (H/L) Ratio

In the 3rd, 6th, 9th and 12th laying month approximately 36 laying hens were randomly

chosen from each housing system, considering group sizes and perch position (small group

housing system) to equal parts (430 hens in total). In EV 625a-EU, 4 compartment variants

related to the different group sizes and perch positions (60 hens, BE, ST and 40 hens BE, ST)

with 2 replicates each per tier were tested. In Aviplus, compartments tested had 8 replicates

(top tier), 12 replicates (medium tier) and 24 replicates (bottom tier). Hens were carried to a

separate room and blood was immediately taken from a wing vein. At least 2 blood smears

per hen were prepared within 30 minutes following blood sampling. Blood smears were fixed

in methanol (70 %) and stained using Wright-Giemsa stains. An average number of 480

leucocytes, including heterophils, lymphocytes, monocytes, eosinophils and basophils was

counted on each slide and proportions of white blood cells were calculated. The H/L ratio was

calculated by dividing the relative numbers of heterophils by the relative numbers of

lymphocytes. In addition, hematocrit and layers’ body weight were measured.

Statistical Analysis

Statistical analysis was carried out using the procedure MIXED of SAS, version 9.1.3.

(Statistical Analysis System Institute Inc., Cary, NC, USA, 2006). According to Dixon and

Tukey (1968), a total of six outlier observations for the H/L ratio, which were located at both

69


tails of the distribution, were identified and removed from the data set. After logarithmic

transformation of observed data values, Shapiro-Wilk and Kolmogorov-Smirnow test proved

data to be normally distributed (PROC UNIVARIATE). In the statistical model, housing

system (SYS), group size and perch position (EV) within housing system GR_PP(SYS),

laying month (MON) and the interaction between housing system and laying month

(SYS*MON) were included as fixed effects. Additionally, the interaction

MON*GR_PP(SYS) was included in an extended model to show the differences between

housing systems in the course of the H/L ratio during the laying period. The interaction

between individual compartment within housing system and laying month

(comp(SYS)*MON) was used as randomly distributed effect. Body weight (BW) within

laying month was employed as a covariate. F-test was conducted to test the significance of the

effects in the statistical model. Results of variance analysis were regarded significant when

the error probability was less than 5 % (P < 0.05).

Log-Yijklmn = µ + SYSi + GR_PP(SYS)ij + MONk + SYS*MONik + comp(SYS)*MONikl + b x

BW(MON)km + eijklmn

Log-Yijklmn h/l-ratio or relative proportion of leucocytes

μ model constant

SYSi fixed effect of housing system (i = 1 to 3)

GR_PP(SYS)ij fixed effect of group size and perch position (EV) within housing

system (ij = 1 to 8)

MONk fixed effect of laying month (k = 1 to 4)

SYS*MONik fixed effect of housing system and laying month (ik = 1 to 12)

comp(SYS)*MONikl randomly distributed effect of interaction between individual

compartment within housing system and laying month


BW(MON)km body weight of layers within laying month

eijklmn random error variation

Results

H/L-ratio and relative numbers of heterophils significantly differed among the 3 different

housing systems tested (Table 1). H/L-ratio was significantly lower in hens kept in the small

group system compared to layers housed in furnished cages. Hens in Aviplus had higher H/L-

ratios compared to the aviary system, although differences were not significant (P = 0.075).

70


No differences in H/L-ratio could be detected between layers housed in the aviary system and

EV. Relative numbers of heterophils were significantly higher in hens kept in Aviplus

compared to EV and aviary system, whereas no difference was detected between EV and

aviary system. The corresponding relative number of lymphocytes did not differ among the 3

different housing systems tested. With relation to the different group sizes and perch positions

tested, H/L-ratio was found to be lowest in layers kept in compartments of 40 hens and

perches incorporated in the BE position (EV) and significantly differed from hens kept in

groups of 10, 20 and 30 hens (Aviplus) and from layers kept in compartments of 40 and 60

hens with perches incorporated in the ST position (EV) (Table 1). Furthermore, H/L-ratio in

hens kept in compartments of 40 layers with perches in the BE position was significantly

lower (P = 0.046) compared to hens kept in the aviary system, when the interaction

MON*GR_PP(SYS) was included in the extended statistical model. No differences in H/L-

ratio were found among the different group sizes of layers kept in Aviplus. In EV,

compartments of 40 and 60 layers with perches incorporated in the BE position did not differ

in H/L-ratio and no differences were found between the 2 group sizes and perches installed in

the ST position. H/L-ratio significantly increased from laying month 3 to 12 and 9 to 12. In

the 9th laying month, hens reflected the lowest H/L-ratio of all 4 laying months tested.

Relative numbers of heterophils significantly increased and relative numbers of lymphocytes

significantly decreased from the 3rd to the 12th laying month (Table 1). It was interesting to

note that relative number of eosinophils was highest in layers kept in Aviplus and aviary

system and significantly differed from hens housed in EV. In addition, relative numbers of

eosinophils were significantly lower in compartments of 40 layers with perches in the BE

position compared to layers kept in the aviary system, in the different groups of Aviplus (10,

20, 30 hens) and in compartments of 60 hens with perches incorporated in the BE position.

Discussion

Hens kept in EV showed significantly lower H/L-ratios compared to layers housed in Aviplus.

Layers in EV manifested significant heteropenia and corresponding non-significant

lymphophilia. These results provided evidence that keeping layers in the small group housing

system with elevated perches imposed less environmental stress on hens compared to the

furnished cage system. In contrast to BARNETT et al. (1997a), ELSTON et al. (2000) described

higher H/L-ratios in layers kept in solid-sided cages compared to open-sided cages and traced

these findings back to a possible preference of layers to experience greater visual access to

their surroundings. In both the Aviplus and EV system, compartments were separated by solid

71


side partitions. As compartments of Aviplus were also equipped with solid centre partitions,

this could have contributed to an increased level of stress as visual access was limited. The

level of stress experienced by hens kept in EV (H/L-ratio: 0.269) was comparable to layers

kept in the aviary system (H/L-ratios: 0.267). So far, data on H/L-ratios of layers kept in

aviary systems is very rare. NICOL et al. (2006) analyzed the effect of flock size and stocking

density in a single-tier aviary system but could not detect clear effects on the H/L ratio

between the different treatments, except an increase in H/L-ratio towards the end of the laying

period. As the H/L-ratio is a highly heritable trait (AL MURRANI et al., 1997) and NICOL et al.

(2006) used a different layer line in their investigation, data on H/L-ratio values are not

comparable with the present study. Differences in H/L-ratio between layers kept in Aviplus

and aviary system nearly reached a significant level with hens kept in the furnished cage

system experiencing increased levels of stress. A reduced level of stress in layers kept in the

aviary system compared to Aviplus had been expected, but it was a rather unexpected finding

that differences between EV and Aviplus occurred to an even greater extent. Hens in the

aviary system were provided with occupational material and were given access to a littered

outdoor-area. Increased opportunities to perform natural behavioral traits are certainly an

explanation for less perception of stress. The impact of occupational material was studied by

EL-LETHEY et al. (2000) who detected a reduced H/L ratio in hens kept with straw. The effect

of group size on H/L-ratio was significant between compartments of 10, 20, 30 hens (Aviplus)

and 40 layers (perch position BE, EV) with hens in the smaller pens and not-elevated perches

experiencing a higher stress exposure. KEELING et al. (2003) suggested that hierarchical social

structures in small groups, which bear the potential of social conflicts, break down in larger

groups so that birds develop a tolerant social system. A group of 40 hens might be large

enough to develop non-aggressive social behaviour. Layers kept in compartments of 60 hens

(perch position BE) also showed lower H/L-ratio (0.26) compared to the smaller group sizes

of Aviplus (0.32, 0.30, 0.31), although differences did not achieve a significant level. Apart

from the group size, the different perch positions tested in EV seemed to have a significant

effect on layers’ stress perception. Hens kept in groups of 40 and 60 layers with perches in the

ST position did not differ in H/L-ratios compared to the smaller group sizes of Aviplus.

Perches incorporated in the BE position in groups of 40 hens were found to reduce levels of

stress compared to groups of 40 and 60 hens with perches in the ST position and compared to

hens kept in groups of Aviplus. A possible explanation could be that hens were given

opportunities to perch more secludedly in the back of the compartments, which might have

been favourable. Perches incorporated in the ST position could have led to increased

72


accidental collisions with perches as elevated front and back perches might have been

hindering in layers’ movements. Accidental collisions with perches as a result of social

disruptions could have increased the level of stress due to pain experience. BARNETT et al.

(1997b) analysed H/L-ratios in hens kept in cages equipped with perches and those without

and could not prove any differences, whereas CAMPO et al. (2005) found hens being less

stressed and reflecting lower H/L-ratios when perches were provided compared to cages

without perches. The perch position seemed to play an important role in reducing layers’

stress perception particularly towards the end of the laying period and elevated perches in the

BE variant seemed to prevent best the increase of the H/L ratio in the second half of the

laying period. Generally, hens in groups of 40 (BE, EV) showed lower stress perception in the

second half of the trial period compared to Aviplus and aviary system. Significant differences

between EV (group size 40, BE) and the aviary system were primarily caused by the increase

of the H/L ratio in hens kept in the aviary system towards the end of the laying period. DAVIS

et al. (2000) also described an increase in H/L-value with age related to the egg production

cycle and NICOL et al. (2006) found an increase in H/L-ratio by the end of the lay in hens kept

in single-tier aviaries due to poorer welfare status of layers. Treatment against the red mite

(Dermanyssus gallinae) in the 8th laying month could have contributed to a lower H/L-ratio

in the 9th laying month compared to laying month 6 provided that the infestation had

contributed to stress exposure. Hematocrit of layers did not differ among the different housing

systems and group sizes, suggesting that infestation with the red mite did not accumulate in

any of the systems or group sizes tested. Small group housing systems with elevated perches

are supposed to combine the needs of high hygienic standards that are related to systems

which are well protected from outside environmental influences and improved animal

welfare. Interestingly, we found a significantly lower number of eosinophils in hens kept in

EV compared to the aviary system, which could be an indicator of a generally lower parasitic

exposure as hens in the EV did not have any outdoor access. As hens in Aviplus and EV were

equally protected from external influences, the higher relative number of eosinophils in

Aviplus compared to EV was difficult to explain. Hens in groups of 10, 20 and 30 layers of

Aviplus might have been subjected to increased dust exposure as the smaller compartment

sizes could have led to less air ventilation compared to the larger group sizes of EV. One of

the reasons for increased relative numbers of eosinophils in layers kept in Aviplus might be

due to allergic reactions as a response to dust exposure.

The findings of the current investigation showed that stress levels in layers were strongly

influenced by different housing environments, group sizes, perch positions and laying month.

73


The greatest perception of stress was experienced by layers kept in the furnished cage system.

Keeping laying hens in the small group housing system in groups of 40 layers together with

the back perches being incorporated in an elevated position indicated to impose the least

environmental stress on hens among the different housing environments tested.

Summary

The objective of the present study was to assess the level of stress imposed on Lohmann

Silver laying hens kept in a small group housing system with elevated perches (Eurovent (EV)

625a-EU, group sizes 40, 60 hens, 4 perches with 2 different heights) compared to furnished

cages (Aviplus, group sizes 10, 20, 30 hens) and an aviary housing system (Natura, 2 pens,

1,250 hens) under identical management and feeding conditions. Each 2 perches within

compartments of EV were either incorporated in a stepped position (ST, front and back

perches heightened) or with only the back perches being elevated (BE). In the 3rd, 6th, 9th

and 12th laying month, approximately 36 hens were randomly chosen from each housing

system (430 hens in total) and heterophil to lymphocyte (H/L) ratio was determined. Laying

hens kept in EV had significantly lower H/L ratio compared to hens housed in Aviplus,

whereas no difference was detected between EV and aviary system. Hens kept in groups of 40

layers in compartments with perches in the BE position showed significantly lower H/L-ratios

compared to hens kept in groups of 10, 20, 30 layers (Aviplus) and groups of 40 and 60 hens

with perches incorporated in the ST position. Differences between group size 40 (BE) and the

aviary system nearly achieved the significance level (P = 0.054). Hens kept in furnished cages

reflected the greatest stress exposure. Group sizes of 40 hens together with elevated back

perches were associated with lowest levels of H/L ratios and these ratios were even lower

than in hens kept in the aviary system. Keeping hens in groups of 40 layers together with

perches incorporated in the BE position indicated to be most favourable in terms of imposing

the least environmental stress on layers.

Key words H/L-ratio, stress, furnished cages, small group system with elevated perches,

laying hens

Zusammenfassung

Das Ziel dieser Studie war es, erstmalig die Stressbelastung bei LS Hybriden in

Kleingruppenhaltung mit erhöhten Sitzstangenpositionen (EV 625a-EU, Gruppengrößen 40

und 60 Hennen, hintere Sitzstangen erhöht (HH), vordere und hintere Sitzstangen erhöht und

74


stufig installiert (ST)), ausgestalteten Käfigen (Aviplus, Gruppengrößen 10, 20 und 30

Hennen) und einer Volierenhaltung (Natura, zwei Großgruppen zu je 1,250 Hennen) unter

identischen Managementbedingungen anhand des H/L-Ratios vergleichend zu ermitteln. Am

Ende des 3., 6., 9. und 12. Legemonats wurden jeweils 36 Hennen pro Haltungssystem

zufällig entnommen (insgesamt 430 Hennen) und eine Bestimmung des H/L-Ratios

durchgeführt. Hennen aus Aviplus wiesen einen im Vergleich zur Kleingruppe signifikant

höheren und im Vergleich zur Voliere annähernd signifikant höheren (P = 0,075) H/L-Ratio

auf. Zwischen Tieren aus Volierenhaltung und Kleingruppe hingegen konnte kein

Unterschied im H/L-Ratio festgestellt werden. Hennen aus Kleingruppen (40 Tiere, HH

Variante) zeigten einen signifikant niedrigeren H/L-Ratio im Vergleich zu Hennen aus

Kleingruppen (ST Variante) und zu Hennen aus ausgestalteten Käfigen (10, 20 und 30 Tiere).

Die Unterschiede im H/L-Ration von Tieren aus der Kleingruppe (40 Hennen, Variante HH)

im Vergleich zum Volierenhaltungssystem erreichten annähernd Signifikanz (P = 0,054). Bei

einer Erweiterung des statistischen Modells wiesen Hennen aus der Kleingruppe

(Gruppengröße 40, Variante HH) gegen Ende der Legeperiode einen signifikant niedrigeren

H/L-Ratio auf als Tiere aus Volierenhaltung. In allen drei Haltungssystemen wurde ein

signifikanter Anstieg des H/L-Ratios vom 3. zum 12. Legemonat festgestellt. Hennen aus

Kleingruppen (Gruppengröße 40, Variante HH) zeigten insbesondere gegen Ende der

Legeperiode einen geringeren H/L-Ratio. Die Sitzstangenvariante HH (40 Hennen) schien

einen sehr positiven Einfluss auf eine ungestörte Sitzstangennutzung auszuüben und der in

diesem Haltungssystem gemessene niedrigere H/L-Ratio deutet auf eine geringere

Stressbelastung hin.

Stichworte H/L-Ratio, Stress, ausgestalteter Käfig, Kleingruppenhaltung mit erhöhten

Sitzstangen, Legehennen

75


References

AL-MURRANI, W. K., A. KASSAB, H. Z. AL-SAM and A. M. AL-ATHARI, 1997:

Heterophil/lymphocyte ratio as a selection criterion for heat resistance in domestic fowls.

Br. Poult. Sci. 38, 159-163.

AL-MURRANI, W. K., A. J. AL-RAWI, M. F. AL-HADITHI and B. AL-TIKRITI, 2006: Association

between heterophil/lymphocyte ratio, a marker of ‘resistance’ to stress and some

production and fitness traits in chickens. Br. Poult. Sci. 47, 443-448.

BARNETT, J. L., P. C. GLATZ, E. A. NEWMAN and G. M. CRONIN, 1997a: Effects of modifying

layer cages with solid sides on stress physiology, plumage, pecking and bone strength of

hens. Austr. J. Exp. Agric. 37, 11-18.

BARNETT, J. L., P. C. GLATZ, E. A. NEWMAN and G. M. CRONIN, 1997b: Effects of modifying

layer cages with perches on stress physiology, plumage, pecking and bone strength of hens.

Austr. J. Exp. Agric. 37, 523-529.

CAMPO, J. L., M. G. GIL, S. G. DÁVILA and I. MUÑOZ, 2005: Influence of perches and footpad

dermatitis on tonic immobility and heterophil to lymphocyte ratio of chickens. Poult. Sci.

84, 1004-1009.

DAVIS, G. S., K. E. ANDERSON and A. S. CARROLL, 2000: The effects of long-term caging and

molt of single comb white leghorn hens on heterophil to lymphocyte ratios, corticosterone

and thyroid hormones. Poult. Sci. 79, 514-518.

DIXON, W. J. and J. W. TUKEY, 1968: Approximate behavior of the distribution of Winsorized

t: Trimming/Winsorization II. Technometrics 10, 83.

EL-LETHEY, H., V. AERNI, T. W. JUNGI and B. WECHSLER, 2000: Stress and feather pecking in

laying hens in relation to housing conditions. Br. Poult. Sci. 41, 22-28.

ELSTON, J. J., M. BECK, M. A. ALODAN and V. VEGA-MURILLO, 2000: Laying hen behaviour

2. Cage type preference and heterophil to lymphocyte ratios. Poult. Sci. 79, 477-482.

GROSS, W. B. and H. S. SIEGEL, 1983: Evaluation of the heterophil/lymphocyte ratio as a

measure of stress in chickens. Avian Dis. 27, 972-979.

KEELING, L. J., I. ESTEVEZ, R. C. NEWBERRY and M. G. CORREIA, 2003: Production-related


group sizes. Poult. Sci. 82, 1393-1396.

NICOL, C. J., S. N. BROWN, E. GLEN, S. J. POPE, F. J. SHORT, P. D. WARRISS, P. H. ZIMMERMAN

and L. J. WILKINS, 2006: Effects of stocking density, flock size and management on the

welfare of laying hens in single-tier aviaries. Br. Poult. Sci. 47, 135-146.

76


SAS, 2006: Statistical Analysis System, Version 9.1.3, SAS Institute Inc., Cary, North

Carolina, USA.

Correspondence:

Ottmar Distl, Insitute of Animal Breeding and Genetics, University of Veterinary Medicine

Hannover, Bünteweg 17p, 30559 Hannover, Germany, Tel.: 0049-511-953-8875; Fax: 0049-

511-953-8582; e-mail: [email protected].

77


Table 1. Logarithmized LS-Means (LSMlog), their standard errors (SElog), LSMlog re-

transformed (LSM), their 95% confidence intervals (CI95) and significant differences between

the different housing systems, group sizes, perch positions (Eurovent (EV) 625a-EU) and

laying months for H/L ratios and relative proportions of heterophils, lymphocytes and

eosinophils (%).

Logarithmierte LS-Mittelwerte (LSMlog), ihre Standardfehler (SElog), rücktransformierte LSMlog

(LSM), ihre 95% Konfidenzintervalle (CI95) und signifikante Unterschiede zwischen den

verschiedenen Haltungssystemen, Gruppengrößen, Sitzstangenpositionen (Eurovent (EV) 625a-

EU) und Legemonaten für den H/L-Ratio und prozentuale Anteile der heterophilen

Granulozyten, Lymphozyten und eosinophilen Granulozyten (%).

H/L ratio Heterophils (%) Lymphocytes (%) Eosinophils (%) Trait LSMlog SElog

LSM CI95

LSMlog SElog

LSM CI95

LSMlog SElog

LSM CI95

LSMlog SElog

LSM CI95

Housing systems Aviplus -1.18a

0.05 0.31

0.28-0.34 3.04a

0.04 21.0

19.5-22.54.22a 0.01

68.1 66.3-70.0

-0.04A 0.07

1.0 0.8-1.1

EV -1.31b 0.05

0.27 0.24-0.30

2.94b 0.04

18.9 17.5-20.3

4.25a 0.01

70.3 68.3-72.3

-0.32B 0.07

0.7 0.6-0.8

Aviary -1.32ab 0.06

0.27 0.24-0.30

2.93b

0.05 18.6

17.0-20.44.25a 0.02

69.8 67.4-72.3

-0.10a 0.08

0.9 0.8-1.1

Group sizes in Aviplus (10, 20, 30), EV (40-BE, 40-ST, 60-BE, 60-ST) and Aviary system 10

-1.15A 0.08

0.32 0.27-0.37

3.06A 0.06

21.3 18.9-23.9

4.21A 0.02

67.1 64.2-70.2

-0.02A 0.12

1.0 0.8-1.2

20

-1.21AB 0.08

0.30 0.25-0.35

3.03AB 0.06

20.6 18.3-23.3

4.24ab 0.02

69.5 66.3-72.7

0.04A 0.12

1.0 0.8-1.3

30

-1.17AB 0.09

0.31 0.26-0.37

3.05AB 0.06

21.0 18.6-23.8

4.22a 0.02

67.7 64.5-71.0

-0.13a 0.11

0.9 0.7-1.1

40-BE

-1.55C

0.10 0.21

0.17-0.26 2.75C 0.07

15.7 13.5-18.1

4.31B 0.03

74.1 70.0-78.4

-0.57B 0.14

0.6 0.4-0.7

40-ST

-1.21a 0.10

0.30 0.25-0.36

3.02A 0.07

20.5 17.7-23.7

4.23ab 0.03

68.6 64.9-72.5

-0.24ab 0.13

0.8 0.6-1.0

60-BE -1.34ac 0.10

0.26 0.21-0.32

2.92ac 0.07

18.6 16.1-21.6

4.26ab 0.03

70.9 67.0-75.0

-0.15ac 0.14

0.9 0.7-1.1

60-ST -1.16A 0.10

0.31 0.26-0.38

3.05A 0.07

21.2 18.3-24.4

4.22a 0.03

67.7 64.1-71.6

-0.31ab 0.14

0.7 0.6-1.0

1,250 (Aviary)

-1.32ac 0.06

0.27 0.24-0.30

2.93a 0.05

18.6 17.0-20.4

4.25ab 0.02

69.8 67.4-72.3

-0.10A 0.08

0.9 0.8-1.1

Laying month 3

-1.31b 0.07

0.27 0.23-0.31

2.94b 0.05

19.0 17.1-21.0

4.26a 0.02

70.7 68.0-73.5

-0.36B 0.10

0.70 0.58-0.84

6

-1.25ab 0.06

0.29 0.25-0.32

2.98ab 0.05

19.6 17.9-21.5

4.23ab 0.02

68.9 66.5-71.3

-0.20ab 0.08

0.82 0.70-0.97

78


79

Table 1 continued.

H/L ratio Heterophils (%) Lymphocytes (%) Eosinophils (%) Trait LSMlog

SElog LSM CI95

LSMlog SElog

LSM CI95

LSMlog SElog

LSM CI95

LSMlog SElog

LSM CI95

Laying month 9

-1.41B 0.06

0.24 0.22-0.28

2.85B 0.05

17.4 15.8-19.0

4.27a 0.02

71.3 68.8-73.9

-0.01A 0.09

0.99 0.83-1.17

12

-1.10aA 0.06

0.33 0.29-0.38

3.10aA 0.04

22.2 20.4-24.3

4.20b 0.02

66.8 64.6-69.1

-0.03a 0.08

0.97 0.83-1.13

ST: both perches heightened and in stepped position; BE: back perch elevated; means within a

column with no common supercscipts differ (lowercase superscripts: P < 0.05; uppercase

superscripts: P < 0.01).

ST: beide Sitzstangen erhöht, stufige Position; BE: hintere Sitzstange erhöht; LS-Mittelwerte

innerhalb einer Spalte ohne gemeinsamen Index unterscheiden sich signifikant

(Kleinbuchstabe: P < 0.05; Großbuchstabe: P < 0.01).

Chapter VI

Keel bone condition in laying hens: a histological evaluation of

macroscopically assessed keel bones

B. Scholz, S. Rönchen, H. Hamann, M. Hewicker-Trautwein and O. Distl

Berliner Münchener Tierärztliche Wochenschrift

Chapter VI: Histological evaluation of keel bone

Britta Scholz1, Swaantje Rönchen1, Henning Hamann1, Marion Hewicker-Trautwein2 and

Ottmar Distl1

1Institute for Animal Breeding and Genetics, 2Institute for Pathology, University of

Veterinary Medicine Hannover (Foundation), Hannover, Germany

Keel bone condition in laying hens: a histological evaluation of

macroscopically assessed keel bones Brustbeinstatus bei Legehennen: eine histologische Untersuchung makroskopisch beurteilter

Brustbeine

Running title: Histological evaluation of keel bone

Laufende Überschrift: Histologische Untersuchung des Brustbeins

Corresponding author: Ottmar Distl, Institute for Animal Breeding and Genetics, University

of Veterinary Medicine Hannover (Foundation), Bünteweg 17p, 30559 Hannover, Germany,

Tel.: +49 511 953 8875; Fax: +49 511 953 8582; E-mail: [email protected]

82


Summary

The objective of the present study was to conduct a corresponding histological analysis of 162

macroscopically assessed keel bones (1: severe, 2: moderate, 3: slight, 4: no deformity). Four

layer lines were used and hens were kept in furnished cages, small group systems (both

allowing more activities due to the provision of perches) and an aviary system, which fully

conformed to the EU standards. Investigations were carried out in the 3rd, 6th, 9th and 12th

laying month of two experimental trials. In 97.9 % of grade 4 keel bones, no histological

deviations were found, whereas in keel bones manifesting deformities of grade 1 and 2, the

predominant histological observation was the incidence of fracture callus material (FCM) and

new bone in the form of woven bone. FCM was also detected in 50.9 % of grade 3 keel bones,

whereas in 40.7 %, only s-shaped deviations of keel bones were found, which were related to

extended pressure loading while perching activities rather than short-duration trauma.

Histological analysis showed that keel bones of grade 1 and 2 were mainly attributed to

traumatic origin and therefore associated with pain experience in layers. Grade 3 keel bones

manifested either FCM as a result of trauma or adaptational deformities without any evidence

of a preceding fracture in response to mechanical pressure loading and were most likely not

associated with pain. Therefore, histological analysis was found to be a mandatory tool when

evaluating grade 3 keel bones with respect to layers’ welfare.

Key words: Keel bone condition, laying hen, histological evaluation, welfare

Zusammenfassung

Ziel dieser Studie war es, bei 162 makroskopisch beurteilten Brustbeinen (1 = hochgradig, 2 =

mittelgradig, 3 = geringgradig verändert, 4 = ohne besonderen Befund) von Legehennen, die

in mit Sitzstangen ausgestatteten, ausgestalteten Käfigen, Kleingruppen- und Volierenhaltung

gehalten wurden, eine überprüfende, histologische Untersuchung durchzuführen. Es wurden

vier Legelinien verwendet und die Untersuchungen erfolgten im 3., 6., 9. und 12. Legemonat.

In 97.9 % der mit Grad 4 beurteilten Brustbeine konnten auch histologisch keine

Abweichungen gefunden werden, während Brustbeine mit Deformationen von Grad 1 und 2

überwiegend Frakturkallus (FK) und Knochenneubildung (Geflechtknochen) aufwiesen. FK

wurde auch in 50.9 % der mit Grad 3 beurteilten Brustbeine gefunden, während 40.7 % nur s-

förmige Verbiegungen, vermutlich als Anpassungsreaktion des Knochens auf kontinuierliche,

mechanische Belastung während der Sitzstangennutzung, aufwiesen. Die histologische Studie

zeigte, dass deformierte Brustbeine von Grad 1 und 2 in erster Linie traumatischer Genese

83


waren. Brustbeine von Grad 3 hingegen wiesen entweder traumatisch bedingten FK oder

lediglich Formänderungen in der Knochenstruktur auf, die vermutlich nicht akuter,

schmerzhafter Natur waren. Die makroskopische Beurteilung von geringgradig veränderten

Brustbeinen im Hinblick auf Wohlergehen, insbesondere Schmerzempfindung, bei Hennen

wurde ohne histologische Untersuchung als unzureichend angesehen.

Schlüsselwörter: Brustbeinstatus, Legehennen, histologische Beurteilung, Wohlergehen

Introduction

Increased awareness of laying hen welfare has led to major changes in policies on laying hen

husbandry. Due to the EU directive passed in 1999 (CEC, 1999) conventional cages have to

be replaced by furnished cages or alternative housing systems by the end of 2011 in all

European countries. As the German legislation has put through the abolition of furnished

cages after 2011, research on housing systems that are appropriate to layers is strongly

required. In the process of developing advanced husbandry systems, evaluation of layers’ keel

bone is an important criterion, which has been included in a variety of studies on welfare of

laying hens kept in a particular housing system. The provision of increased possibilities to

move is a major issue in newly-developed house keeping systems as movement is supposed to

strengthen layers’ skeleton, thus reducing the risk of osteoporosis. Keel bone of layers is not

only affected by general inactivity osteoporosis but is also very vulnerable to deformities and

fractures due to its exposed anatomical location. In a variety of ongoing studies on evaluating

keel bone condition of layers kept in different house keeping systems (Elson and Croxall,

2006; LayWel EU-project, 2006), only macroscopic findings on keel bone status have been

included. Applying macroscopic evaluation techniques on assessing keel bone, studies have

shown that keel bone condition is a widely-spread problem in laying hen husbandry. In a

study by Freire et al. (2003), 73 % of hens housed in an aviary system produced keel bone

deformities at the end of the laying period. Furnished cages with incorporated perches are

more likely to produce keel bone deformities in layers than conventional cages. Vits et al.

(2005) found keel bone deformities in 33% of hens kept in furnished cages, thus

demonstrating a prevalent welfare problem related to this type of housing system. A scoring

scheme for macroscopic evaluation of keel bone ranging from score 1 (severe deformity) to 4

(no deformity) has been used in a variety of investigations (Elson and Croxall, 2006; Vits et

al., 2005; Weitzenbürger et al., 2006). So far, no data exist on the severity code of keel bone

deformities (no deformity, slight, moderate, severe deformity) and the underlying histological

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findings of layers kept in housing systems which fully conformed to the EU legislative

standards on keeping laying hens. In a study by Fleming et al. (2004) fracture callus material

and development of new bone was detected in all cases of macroscopically deviated keel

bones in ISA, Hy-line and LSL White Leghorn hybrids kept in battery or free-range systems,

thus proving a traumatic cause. The aim of the present study was to analyse the histological

appearance of keel bone deformities representing the different macroscopically reported

severity codes. The study comprised four different commonly used layer lines (Lohmann

Silver, Lohmann Tradition, Lohmann Selected Leghorn, Lohmann Brown), which were kept

in furnished cages, small group systems and an aviary system.

Materials and Methods

Farms, housing systems and layer lines

The study was conducted over two experimental trials, each comprising a period of 12

months. Laying hens were kept in six different house keeping systems (Big Dutchman,

Vechta, Germany), which were located at two experimental farms. A three-tier, double-sided

furnished cage system (Aviplus, groups of 10, 20 and 30 layers, non-elevated perches), a

three-tier small group housing system (Eurovent (EV) 625a-EU (EVa), groups of 40 and 60

hens) and an aviary housing system with connected outdoor area (model Natura, three-tier

central block, 2 groups, 1,250 layers) were installed at farm A. In the first trial, layer lines

used were Lohmann Silver (LS) and Lohmann Tradition (LT). In the second trial, only LS

were used. Farm B contained two four-tier, double-sided furnished cage systems (Aviplus,

groups of 10 and 20 hens, non-elevated perches; EV 625A-EU (EVA), 20 and 30 layers) and

a four-tier small group housing system (EVa, 40 and 60 hens). Laying strains kept were

Lohmann Selected Leghorn (LSL) and Lohmann Brown (LB) in the first trial and LSL in the

second trial. A total number of approximately 5,500 hens (Farm A) and 9,000 layers (Farm B)

was kept per trial. All systems tested in the present study fully met the EU legislative

standards on keeping laying hens (EU directive 1999/74/EG). Compartments of Aviplus and

EV systems were equipped with perches, nest boxes, dust bathing areas, devices to shorten

claws and provided 750 cm² space/hen. Unlike the aviary system, Aviplus and EV systems

did not provide outdoor access. Perches within a certain percentage of EVa and EVA

compartments were incorporated at two different heights, thus meeting the legal requirements

on the currently approved small aviary system. In compartments of EVA, either back or front

perches were heightened, whereas in compartments of EVa, either back, front or both perches

were incorporated in an elevated position (Fig.1).

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Perch design

Perches in Aviplus and EV systems were made out of white, polished plastics (PVC, rigid)

and produced a thickness of 30 mm. They were oval shaped with a flattened top and

underside and provided a contact area of 20.1 mm for the layers’ feet. Front and back part

were formed in a convex shape. In EV 625a-EU systems, perches which were modified in

their height, were roundly shaped and made out of abraded, galvanised zinc.

Management and feeding

Hens were subjected to identical management and feeding conditions within each farm.

Layers of farm A (floor reared) and farm B (reared in cages) were transferred to the particular

farm and housing system at the age of 18 weeks. At both farms, a standard diet for laying

hens was provided. Analysis of food components was conducted in regular intervals in order

to monitor the nutritional value of the diet. Layers were subjected to a commonly accepted

prophylactic immunisation scheme for laying hens.

Macroscopic and histological examination of keel bone

On farm A, keel bone status was examined in the 3rd, 6th, 9th and 12th laying month of both

trials. Considering layer strain (first trial) and housing system to approximately equal parts, a

total number of 910 layers was randomly chosen and slaughtered. On farm B, keel bone status

was recorded in the 6th and 12th laying month and 576 hens were included in the study from

farm B (192 hens per each housing system). In total, 1,486 macroscopically examined keel

bones provided the pool for selecting samples for histological analysis. Keel bone of layers

was evaluated visually and per palpation alongside the keel after removal of the skin and its

macroscopic appearance was classified using the following scoring scheme: score 4 = no

deformity, score 3 = slight, score 2 = moderate and score 1 = severe deformity. In the first

trial, histological samples of keel bone were taken in laying month 6, 9, 12 (Farm A) and

laying month 6, 12 (Farm B). In the second trial, samples were taken in all 4 laying months

tested (Farm A) and in laying month 6 and 12 (Farm B). Samples were chosen to cover the

whole range of macroscopic findings on keel bone status to approximately equal parts.

Sampling did not consider layer strain or housing system. A total of 162 samples was taken

for histological analysis. Table 1 provides the numbers of histological samples taken for

analysis by severity code and the random distribution on housing system and layer line within

each farm. Keel bones were removed of breast muscle and tendons and with help of two

transversal cuts through corpus sterni, a 3 mm thick sample of keel bone was excised. The

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location of sampling unaltered keel bones was about 1 cm caudal of the pilae carinae and apex

sterni. Samples of keel bones exhibiting deformities were taken out of the particular area

affected. Tissue samples were fixed for at least 24 hours in formalin (10 %). After

decalcification in HNO3 (5 %) solution for 20 minutes, samples were dewatered and

incorporated into paraffin wax. Histological sections (2-3 µm) were produced using a rotation

microtom (Reichert-Jung 2030, Biocut) and stained with haematoxylin and eosin. Histological

sections were examined and categorised using the following scheme:

0: No evidence of fracture callus material or development of new bone (woven bone)

1: Periostal ectostosis appearing as a thin layer alongside the bone without evidence of a

preceding fracture

2: Appearance of new bone (woven bone) with the keel bone either showing a continous

compacta or a disordered integration of compacta and woven bone, suggesting a preceding

incidence of bone fracture

3: Fracture callus material (woven bone) as a result of bone fracture, still representing a clear

dislocation of bone fragments.

Statistical analysis

Fisher’s exact test (SAS, 2006) was performed in order to determine the significance of the

association between macroscopic scoring of keel bone and related histological findings.

Results

The results of histological findings related to the different severity codes of keel bone

deformities are presented in Table 2. Results of Fisher’s exact test showed significant

differences between macroscopic scoring and histological findings on keel bone (P < 0.001).

In 97.92 % of keel bones evaluated with score 4, pathological deviations in keel bone

structure could not be detected in corresponding histological analysis (Fig. 2a) and in only

one keel bone (2.08 %), development of periostal ectostosis (PE) appearing as a thin layer

alongside the cortical bone, was found (Fig. 3). In 40.68 % of slightly deformed keel bones

(Fig. 5) no evidence of fracture callus material (FCM) or development of new bone (woven

bone) could be observed, whereas deformities in shape without occurrence of new bone

(woven bone) were present (Fig. 2b). In 50.85 % of keel bones scored with 3, either FCM

together with clearly-defined dislocation of bone fragments (10.17 %) (Fig. 5) or appearance

of FCM and new bone, suggesting a preceding bone fracture (40.68 %) could be detected. In

8.47 % of slightly deformed keel bones, cortical bone was accompanied by PE. Histological

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analysis of keel bones evaluated with score 2 (Fig. 4) revealed new bone (woven bone) and

FCM in 80 % of keels. PE and keel bones without any development of new bone (woven

bone) or FCM were detected in 10 % of keel bones in each case. In all keel bones reflecting

severe deformities, appearance of new bone (73.33 %) or new bone together with FCM still

representing the dislocation of bone fragments, was found (26.67 %).

Discussion

Macroscopic evaluation of keel bone according to the applied scoring scheme from 1 to 4 was

found to be a reliable method related to keel bones reflecting either no deformities or modest

to severe deviations. In keel bones scored with 4, histological analysis mirrored very well the

macroscopic findings as the incidence of FCM and development of new bone (woven bone)

could not be observed. In very few cases, cortical bone was found to be extended and in one

keel bone, new bone in the form of PE, which appeared as a thin layer alongside the cortical

bone, was found. In contrast to mammals, birds preferably develop endosteal callus instead of

periostal callus after having stabilized bone lesions (Schmidt et al., 2003). Therefore, the

incidence of PE without visible endosteal callus formation most probably represented a

process of providing structural support to the cortical bone without a preceding bone fracture.

As it is generally known that skeletal tissue represents a very reactive tissue, bone formations

such as cortical bone broadening and thin PE are most probably physiological responses of

bone tissue to external mechanical forces. In contradiction to Fleming et al. (2004), FCM and

development of new bone could not be detected in all cases of macroscopically deformed keel

bones. Histological analysis of keel bones reflecting slight deformities either manifested the

incidence of FCM or did not provide any evidence of FCM or PE development and revealed

s-shaped deformities without any osteal proliferation in the form of new bone (woven bone).

These findings were detected in keel bones of all four laying strains tested, thus suggesting

that the different layer strains did not have an influence on these histological observations.

Laying hens investigated by Fleming et al. (2004) were either kept in battery cages with no

access to perches or in free range systems. Therefore, hens could not have experienced long-

term pressure on the keel bone due to extended perching activities and all kinds of deformed

keel bones observed by Fleming et al. (2004) were related to traumatic origin. In the present

study, histological keel bone analysis of hens kept in housing systems which allow more

activities was conducted for the first time and findings seemed to be strongly impacted by the

provision of perches. Keel bone tissue most probably adapted to extended pressure loading

resulting from frequent use of perches and s-shaped deformities were developed without

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incidence of bone fracture in 40.68 % of layers reflecting slight keel bone deformities and in

10 % of layers exhibiting moderate deformations. As the corpus sterni was found to be very

thin and therefore rather bendable in some layers, it was difficult to describe the extent of the

s-shaped deformities observed in histological analysis to a more precise extent. Keel bone in

all four layer strains supposedly differed in its consistency due to the hens’ age and degree of

keel bone calcification, with keel bones in younger hens being more flexible. This might have

contributed to a gradual adoption of deformities in layers’ keel bone shape as a response to

extended perching activities and pressure loading. Palmer (1993) described the final molding

of a bone’s shape being subservient to the demands of function and directed by pressure and

tension. As a result, abnormal stressors on a growing bone lead to changes in a bone’s shape.

Most observations of slightly deformed keel bones without evidence of FCM were detected in

laying month 12, thus showing that changes in the shape of keel bone seemed to be a

protracted process. Wahlström et al. (2001) made extended perching activities and the long-

term pressure on keel bone responsible for deformities occurring in hens kept in furnished

cages, but so far, histological proof on the nature of these deformities had not been provided.

Fleming et al. (2004) examined keel bones solely at the end of the lay (70 weeks) and found

evidence of FCM in all cases of keel bones reflecting less severe deviations. These results

supported the idea that the present histological findings on deformed keel bones without

evidence of FCM were closely related to the provision of perches and would not have

occurred if layers had been kept in conventional cages or free range systems. However, in

50.85 % of layers exhibiting slightly deformed keels, FCM was observed, thus reflecting a

traumatic origin. Gentle (2001) found evidence of complex pain perception in chickens and

traumatic fractures are strongly related to pain experience in layers. The incorporation of

perches, particularly perches installed at two different heights, could have born an increased

risk of accidental collision with keel bone and therefore led to the high incidence of keel bone

fractures observed in histological analysis, rather than the incidence of general osteoporosis.

In a study by Appleby et al. (1993), 43% of hens kept in furnished cages suffered from keel

bone alterations in comparison to 4% of their counterparts kept in conventional cages, thus

providing evidence of a high frequency of deformed keels in cages with perches. Fleming et

al. (2004) found keel bone fractures in hens kept without provision of perches and related

these findings to the onset of osteoporosis and therefore loss of bone with age. In the present

study, hens were kept in enriched housing systems which fully conformed to the EU

legislative standards on keeping laying hens and were therefore offered more possibilities to

move. Increased movement supposedly contributed to strengthen layers’ skeleton in general,

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which could have alleviated the incidence of osteoporosis in the present study and therefore

the occurrence of keel bone fractures to an even greater extent in slightly deformed keel

bones. As keel bone is very vulnerable due to its exposed anatomical location, lean shape and

mechanical pressure loading, both furnished and small group systems did not succeed in

strengthening layers’ skeleton to an extent that alterations in keel bone’s shape could be fully

prevented. However, a great part of deformities found in slightly deformed keel bones might

not have caused pain in layers due to its non-traumatic origin.

A number of 8 % of slightly and 10 % of moderately deformed keel bones exhibited PE,

which occurred as a thin layer alongside the cortical bone without evidence of a preceding

fracture. It was interesting to note, that PE mainly appeared in slight and moderate keel bone

deformities and were nearly solely found in LSL layers, except in one case of LB hybrid. LSL

layers are of a lighter body weight compared to the other laying strains used in the

investigation. Therefore, LSL layers might be genetically predisposed to develop these kinds

of bone proliferations more frequently in order to structurally support their keel bone. In

addition, 80 % of PE findings occurred in keel bones sampled in laying month 12 and 20 % of

PE findings resulted from keels sampled in laying month 6, thus suggesting an extended

period of time for these formations to develop. In 80 % of keel bones exhibiting moderate and

in all keel bones reflecting severe deformities, development of new bone (woven bone) or

FCM was detected. Keel bone deformities classified as ‘severe’ generally occurred to a less

extent compared to moderate or slight deviations. Samples for histological analysis were

randomly selected according to the macroscopic findings present in the particular laying

month and did not consider layer line or housing system. Most severely deformed keel bones

derived from hens kept in the aviary system and keels reflected FCM or woven bone in all

cases. Histological findings on severely deformed keel bones were therefore primarily related

to traumatic fractures due to flight and landing accidents in the aviary system or perch

collisions and inability to negotiate perches properly in the furnished cages and small group

systems.

The findings of the present study showed that histological analysis of keel bone well agreed to

the macroscopic evaluation related to the grades 4, 2 and 1. In approximately 40 % of slightly

deformed keel bones (grade 3), deviations without development of FCM were observed.

These findings seemed to be strongly related to mechanical pressure loading on the keel bone

due to extended perching activities in furnished and small group housing systems and most

probably did not result from short duration trauma. Unlike traumatic fractures, these bone

remodelling processes in keel bone might not necessarily have produced pain in layers. As

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approximately 50 % of slightly deformed keel bones showed clear incidence of FCM in

histological analysis, it was found impossible to draw a conclusion on slightly deformed keel

bones with respect to layers’ welfare without a corresponding histological analysis.

Acknowledgement

The authors would like to thank Big Dutchman GmbH, Lohmann Tierzucht GmbH and


References

Appleby, M., S.F. Smith, B.O. Hughes (1993): Nesting, dust bathing and perching by laying

hens in cages: effects of design on behaviour and welfare. Br. Poult. Sci. 34, 835-847.

CEC (1999) Richtlinie 1999/74/EG des Rates vom 19. Juli 1999 zur Festlegung von

Mindestanforderungen zum Schutz von Legehennen, ABl. EG Nr. L 203, 53.

Elson, H.A., R. Croxall (2006): European study on the comparative welfare of laying hens in

cage and non-cage systems. Arch. Geflügelk. 70, 194-198.

Fleming, R.H., H.A. McCormack, L. McTeir, C.C. Whitehead (2004): Incidence, pathology

and prevention of keel bone deformities in the laying hen. Br. Poult. Sci. 35, 651-662.

Freire, R., L.J. Wilkins, F. Short C.J. Nicol (2003): Behaviour and welfare of individual

laying hens in a non-cage system. Br. Poult. Sci. 44, 22-29.

Gentle, M.J. (2001): Attentional shifts alter pain perception in the chicken. Anim. Welf. 10,

187-194.

LayWel EU-project (2006): Welfare implications of changes in production systems for laying

hens: a European project. [Work package 3]. www.laywel.eu.

Palmer, N. (1993): Bones and joints. In Jubb, K.V.F., Kennedy, P.C., Palmer, N., eds.

Pathology of domestic animals. San Diego: Academic Press, 24-26.

SAS Institute (2006): Statistical Analysis System, Version 9.1.3, SAS Institute Inc., Cary,

NC, USA.

Schmidt, R.E., D.R. Reavill, D.N. Phalen, eds. (2003): Pathology of pet and aviary birds.

Ames: Iowa State Press 154.

Vits, A., D. Weitzenbürger, H. Hamann, O. Distl (2005): Production, egg quality, bone

strength, claw length and keel bone deformities of laying hens housed in furnished cages

with different group sizes. Poult. Sci. 84, 1511-1519.

Wahlström, A., R. Tauson, K. Elwinger (2001): Plumage condition and health of aviary-kept

hens fed mash or crumbled pellets. Poult. Sci. 80, 266-271.

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Weitzenbürger, D., A. Vits, H. Hamann, O. Distl (2006): Evaluierung von



Legelinien Lohmann Selected Leghorn und Lohmann Brown. Arch. Tierz. 46, 89-102.

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Table 1. Numbers of keel bone samples taken for histological analysis by macroscopic

severity code, farm, layer line and housing system

n No deformity Slight Moderate Severe Farm A 103 EVa-LS 32 10 13 9 0 EVa-LT 7 2 4 0 1 Aviplus-LS 23 10 9 2 2 Aviplus-LT 11 4 2 4 1 Aviary Natura-LS 27 3 10 8 6 Aviary Natura-LT 3 1 0 0 2 Farm B 59 EVa-LSL 20 5 5 10 0 EVa-LB 2 0 0 0 2 Aviplus-LSL 19 8 9 2 0 Aviplus-LB 7 3 2 2 0 EVA-LSL 6 1 3 2 0 EVA-LB 5 1 2 1 1 EVa = Eurovent 625a-EU; EVA = Eurovent 625A-EU; LS = Lohmann Silver; LT = Lohmann

Tradition; LSL = Lohmann Selected Leghorn; LB = Lohmann Brown

Table 2. Results of histological findings (%) related to macroscopic severity code of keel

bone deformity

Histological findings Macroscopic evaluation n 0 1 2 3 No deformity 48 97.92 2.08 0.00 0.00 Slight 59 40.68 8.47 40.68 10.17 Moderate 40 10.00 10.00 42.50 37.50 Severe 15 0.00 0.00 73.33 26.67 0: No evidence of fracture callus material or development of new bone (woven bone); 1:

Periostal ectostosis appearing as a thin layer alongside the bone without evidence of a

preceding fracture; 2: Appearance of new bone (woven bone) with the keel bone either

showing a continous compacta or a disordered integration of compacta and woven bone,

suggesting a preceding incidence of bone fracture; 3: Fracture callus material (woven bone)

as a result of bone fracture, still representing a clear dislocation of bone fragments

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Figure 1. Cross section of perch positions within the small group systems Eurovent 625a-EU

NE

4

3 2

1

1. central tube for supply of dust bathing substrate 2. back perch 3. front perch 4. nipple drinker

FE ST BE NE: non-elevated perches; FE: front perch elevated; ST: perches in a stepped position; BE: back perch elevated.

Figure 2a. Cross-section of keel bone excised 1 cm caudal of

pilae carinae and apex sterni without evidence of histological

deviation.

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Figure 2b. Keel bone revealing an s-shaped deformity without

evidence of fracture callus material or development of new bone

(woven bone).

Figure 3. Periostal ectostosis appearing as a thin layer

alongside the keel bone (cortical bone) without evidence of

a preceding fracture.

CB: Cortical bone; PE: Periostal ectostosis.

95


96

Figure 4. Fracture callus material (woven bone) as a result

of keel bone fracture, still representing a clear dislocation of

bone fragments.

CB: cortical bone; FCM: fracture callus material; BFD: bone

fragment dislocation.

Figure 5. Slightly (grade 3, left) and moderately

(grade 2, right) deformed keel bones.

Chapter VII

Meta-analysis of welfare, egg quality, production and selected

behavioural traits to evaluate small group housing systems for

laying hens


Züchtungskunde

Chapter VII: Meta-analysis of selected welfare, production and behavioural traits

Meta-Analyse von Gesundheits-, Eiqualitäts- Leistungs- und Verhaltensmerkmalen zur

Beurteilung von Kleingruppenhaltungssystemen für Legehennen

BRITTA SCHOLZ, SWAANTJE RÖNCHEN, H. HAMANN UND O. DISTL1

Institut für Tierzucht und Vererbungsforschung der Stiftung Tierärztliche Hochschule Hannover, Bünteweg 17p, D-30559 Hannover; 1Korrespondierender Autor: [email protected]

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1 Einleitung

Mit Umsetzung der EU-Richtlinie 1999/74/EG zur „Festlegung von Mindestanforderungen

zum Schutz von Legehennen“ in nationales Recht wird in Deutschland die konventionelle

Käfighaltung von Legehennen ab 2008 gänzlich verboten sein. In den übrigen EU-Ländern

dürfen konventionelle Käfige bis 2012 genutzt werden und müssen dann durch ausgestaltete

Käfige oder alternative Haltungssysteme ersetzt werden. Während die deutsche Gesetzgebung

darüber hinaus die Nutzung ausgestalteter Käfige bis 2020 befristet hat, wird derzeit vermehrt

die Entwicklung und praktische Erprobung sogenannter Kleingruppenhaltungen gefördert und

deren Eignung für die Legehennenhaltung untersucht. Die Kleingruppenhaltung stellt zum

jetzigen Zeitpunkt neben der Freiland- und Bodenhaltung ein Haltungssystem dar, welches

den Hennen innerhalb eines geschlossenen Systems einen größtmöglichen

Bewegungsspielraum bietet und somit einen positiven Einfluss auf Gesundheits- und

Leistungsmerkmale erwarten lässt. Kleingruppenhaltungen sowie Bodenhaltungen sind in

Deutschland unbefristet zur Nutzung zugelassen.

Im Rahmen dieser Studie wurde eine Meta-Analyse aus bereits veröffentlichten Studien sowie

eigenen Daten von insgesamt zehn untersuchten Legedurchgängen (Gesamtzahl untersuchter

Hennen: 4.553) und mehreren Legelinien, wie Lohmann Selected Leghorn (LSL), Lohmann

Brown (LB) und Lohmann Silver (LS), durchgeführt. Dabei wurden verschiedene

Haltungssysteme, angefangen von der konventionellen Käfighaltung bis zu der aktuell

diskutierten Kleingruppengruppenhaltung, sowie eine Volierenhaltung, hinsichtlich

ausgewählter gesundheits- und leistungsbezogener Merkmale der Hennen verglichen. Ziel

dieser Studie war es, in einer umfassenden Auswertung darzustellen, inwieweit Einflüsse

durch die technische Weiterentwicklung von ausgestalteten Käfigen zu

Kleingruppenhaltungssystemen auf die ausgewählten Merkmale feststellbar waren und

welche positiven Effekte auf Gesundheit und Leistung der Hennen erzielt werden konnten.

Als Referenzsystem diente eine Volierenhaltung mit Kaltscharrraum bzw. mit zusätzlichem

Auslauf (intensive Auslaufhaltung).

2 Material und Methoden

2.1 Legedurchgänge und Datenherkunft

Die in die Meta-Analyse einbezogenen Untersuchungsdaten wurden im Zeitraum 1999 bis

2006 im Legehennenstall des Lehr- und Forschungsgutes (LuFG) Ruthe der Stiftung

Tierärztliche Hochschule Hannover sowie im Versuchsstall (VS) Wesselkamp der Deutschen

Frühstücksei GmbH in Ankum, Kreis Osnabrück, erhoben. Die Meta-Analyse beinhaltete

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insgesamt zehn Legedurchgänge (LD) und eine Gesamtzahl von 4.553 untersuchten Hennen

unter Einbezug der Studien von LEYENDECKER et al. (2001a; 2001b; 2005; unveröffentlichte

Daten (2002/2003)), VITS et al. (2005), WEITZENBÜRGER et al. (2005; 2006a; 2006b), SCHOLZ

et al. (2006) (sowie zur Veröffentlichung eingereichte Daten (LD 2005/2006)) und RÖNCHEN

et al. (2006) (sowie zur Veröffentlichung eingereichte Daten der LD 2004/2005 und

2005/2006) (Tab. 1). Auf dem LuFG Ruthe erfolgten für alle untersuchten Legeperioden pro

Legedurchgang stichprobenweise Entnahmen von im Mittel 518 Legehennen im 3., 6., 9. und

12. Legemonat. Im VS Wesselkamp wurden pro Legedurchgang im Mittel 360 Hennen zu

den oben genannten Untersuchungszeitpunkten bzw. nur im 6. und 12. Legemonat (LD

2004/2005 und 2005/2006) zur Untersuchung entnommen. Haltungssysteme, Legelinien und

Untersuchungszeitpunkte wurden jeweils anteilsmäßig mit gleichen Anzahlen untersuchter

Legehennen berücksichtigt. Detaillierte Beschreibungen der untersuchten Haltungssysteme

der in Tab. 1 angeführten Autoren sind den jeweiligen Studien zu entnehmen. Eigene Studien

wurden über zwei LD (2004 bis 2006) jeweils zeitgleich auf dem LuFG Ruthe und VS

Wesselkamp durchgeführt.

2.2 Haltungssysteme und Legelinien der LD 2004 bis 2006

In beiden Versuchsställen waren jeweils drei verschiedene Haltungssysteme für Legehennen

(Hersteller Fa. Big Dutchman, Vechta, Deutschland) installiert. Die Systeme Aviplus (AP)

und Eurovent (EV) 625A-EU stellten zwei Varianten eines ausgestalteten Käfigs dar. Im AP

wurden Gruppengrößen von 10, 20 und 30 Tieren (LuFG Ruthe) bzw. 10 und 20 Tieren (VS

Wesselkamp) gehalten. Der ausgestaltete Käfig Eurovent (EV) 625A-EU war für 20 und 30

Hennen pro Abteil ausgelegt. Das Haltungssystem EV 625a-EU stellte eine

Kleingruppenhaltung für Gruppen von 40 und 60 Hennen dar. Alle untersuchten

Haltungssysteme boten den Hennen eine Grundfläche von mindestens 750 cm2 pro Tier und

erfüllten durch die Ausstattung mit Sitzstangen, Legenestern, Sandbädern und

Krallenabriebsflächen in allen Punkten die erforderlichen Kriterien der EU-Richtlinie 1999/74

für die Haltung von Legehennen. In beiden LD (VS Wesselkamp) sowie im zweiten LD

(LuFG Ruthe) wurden die Sitzstangen innerhalb der Abteile des EV 625a-EU und EV 625A-

EU auf zwei verschiedenen Höhen installiert, um den Hennen zusätzlichen Bewegungsanreiz

und die Möglichkeit des Aufbaumens zu bieten.

Auf dem LuFG Ruthe waren die dreietagig montierten Systeme AP (doppelreihig), Eurovent

625a-EU sowie eine dreietagige Volierenanlage „Natura“ installiert. Die Volierenhaltung

bestand aus zwei Abteilen mit jeweils 1.215 Legehennen (3,650 x 15,980 mm Grundfläche

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pro Abteil) und separaten, angegliederten Außenscharrräumen (20.980 x 3.400 mm

Grundfläche). Die im ersten LD eingestallten 5.430 Legehennen setzten sich zu gleichen

Teilen aus den Legelinien Lohmann Silver (LS) und Lohmann Tradition (LT) zusammen. Im

zweiten LD wurden nur LS eingestallt. Im VS Wesselkamp standen die über vier Etagen

installierten Systeme AP, EV 625A-EU (beide doppelreihig) sowie EV 625a-EU zur

Verfügung. Im ersten LD wurden etwa 4.500 Lohmann Selected Leghorn (LSL) und 4.500

Lohmann Brown (LB) eingestallt. Im zweiten LD wurden bei gleicher Tierzahl nur LSL

verwendet.

2.3 Gesundheitsmerkmale der LD 1999 bis 2006

Zur Bestimmung des Gesundheitsstatus der Legehennen wurden die Merkmale Humerus- und

Tibiaknochenfestigkeit, Brustbein-, Fußballen- und Gefiederstatus berücksichtigt. Während

der gesamten Versuchsdauer wurden alle Merkmale von den jeweiligen Autoren mit

identischen Geräten (Knochenbruchfestigkeit) sowie anhand identischer

Untersuchungsprotokolle (Brustbein, Fußballen, Gefieder) erhoben. Die Bestimmung der

Humerus- und Tibiaknochenfestigkeit erfolgte bei allen Autoren mit der

Materialprüfmaschine vom Typ „Zwick/Z2.5/TNIS” (Zwick-Roell, Ulm, Deutschland) und

wurde in Newton (N) angegeben. Die Materialprüfmaschine wurde jährlich geeicht und auf

ihre Präzision bei der Messung hin überprüft. Der Brustbeinstatus der Legehennen wurde von

den Autoren anhand einer vierstufigen Punkteskala ermittelt (Note 4 = unverändertes

Brustbein, Note 3 = geringgradige, Note 2 = mittelgradige und Note 1 = hochgradige

Deformation). Zur Beurteilung des Fußballenstatus (Sohle) wurden von jeder Legehenne

beide Füße makroskopisch untersucht. Dabei wurden Hyperkeratosen und Epithelläsionen

getrennt voneinander erfasst. Der Schweregrad des Fußpaares richtete sich nach der

Veränderung mit der stärksten Ausprägung. Zur Befunderhebung wurde ein einheitliches

Beurteilungsschema mit den Schweregraden 1 (keine Hyperkeratose, Epithel intakt, keine

Verdickung des Ballens) bis 4 (großflächige, tiefgreifende Läsionen, Ballen hochgradig

verdickt) bzw. 5 (höchstgradige Hyperkeratose) verwendet. Der Befiederungsstatus wurde

von allen Autoren für die Körperregionen Kopf, Hals, Brust, Bauch, Rücken, Flügel und

Schwanz separat anhand einer Bewertungsskala von 1 (gravierende Gefiederschäden,

federlose Stellen) bis 4 (sehr gutes, vollständiges Gefieder mit nur wenig deformierten oder

beschädigten Federn) bewertet. Zur Ermittlung des Gesamtgefiederstatus wurden die für die

jeweiligen Körperregionen vergebenen Punkte im Anschluss zu einer Gesamtsumme

aufaddiert (max. 28, min. 7 Punkte).

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2.4 Leistungsmerkmale, Eischalenbruchfestigkeit und Mortalität der LD 1999-2006

Neben dem Leistungsmerkmal Legeleistung pro Bestandshenne wurden die Merkmale

Eischalenbruchfestigkeit und Mortalität der Hennen in die Untersuchung einbezogen. Die

Legeleistung der Hennen sowie die Anzahl der verendeten Tiere wurden in beiden

Versuchsställen täglich durch die Tierbetreuer erfasst. Bei allen Autoren erfolgten die

Untersuchungen zur Messung der Eischalenbruchfestigkeit über den gesamten

Versuchszeitraum mit der Materialprüfmaschine vom Typ „Zwick/Z2.5/TNIS”. Die

Untersuchungen wurden einmal pro LM durchgeführt. In den LD 2004-2006 (Ruthe) wurde

jeweils eine Stichprobe von im Mittel 4.389 Eiern, gleichmäßig auf die jeweils zu

untersuchenden Haltungssysteme aufgeteilt, untersucht. Die Anzahl der untersuchten Eier der

Autoren VITS et al. (2005) und LEYENDECKER et al. (2005) sind den angegebenen

Publikationen zu entnehmen.

2.5 Verhaltensmerkmale der LD 2002-2006

Die Verhaltensmerkmale Stehen auf dem Drahtboden, Gehen auf dem Drahtboden,

Aufenthalt auf den Sitzstangen (Stehen und Sitzen), Ruhen auf den Sitzstangen, Sandbaden

auf dem Drahtboden, Pickaktivität im Sandbad, auf Objekte gerichtete Pickaktivität (z.B.

Einrichtungselemente, Drahtboden) und Federpicken wurden während der Lichtphase mittels

Direktbeobachtung und Momentaufnahme erfasst. Zur Methodik der Datenerfassung siehe

WEITZENBÜRGER et al. (2006b). Eigene Verhaltensbeobachtungen erfolgten im 3., 6., 9. und

12. LM (2. LD, LuFG Ruthe), im 6. und 12. LM (1. LD) sowie im 3., 6. und 12. LM (2.LD)

(VS Wesselkamp).

2.6 Statistische Auswertung

Für die Meta-Analyse wurden die LSM aus jedem Legedurchgang pro Ort der Untersuchung,

Haltungssystem und Legelinie (soweit mehrere LL eingesetzt wurden) für Humerus- und

Tibiabruchfestigkeit, Brustbein-, Fußballen- und Gefiederstatus, Legeleistung pro

Bestandshenne, Mortalität, Eischalenbruchfestigkeit sowie für die Verhaltensmerkmale

verwendet. Die dazu gehörigen Studien sind in Tab. 1 angeführt.

Die Meta-Analyse erfolgte anhand eines linearen Weighted Least Square Modells (Prozedur

GLM von SAS mit der Option „weight“). Als Gewichtung wurden die Reziprokwerte der

quadrierten Standardfehler (SE) der zugehörigen LSM verwendet. Die Anzahl der LSM, die

den gewichteten LSM der einzelnen Merkmale jeweils zugrunde liegen, sind in der Legende

zu unten angegebener Formel aufgeführt. Aufgrund einer unterschiedlichen genetischen

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Herkunft der Legelinie Lohmann Silver wurden dem fixen Effekt LIN in dem statistischen

Modell die drei Ausprägungen Braunleger (Lohmann Brown, Lohmann Tradition), Weißleger

(Lohmann Selected Leghorn) und Lohmann Silver zugewiesen. Das Haltungssystem (SYS),

der Ort der Untersuchungen (LuFG Ruthe, VS Wesselkamp) innerhalb des Haltungssystems

(ORT(SYS)), sowie die Legelinie innerhalb des Haltungssystems (LIN(SYS)) wurden als fixe

Effekte in das Modell einbezogen. Insgesamt wurden sechs verschiedene Haltungssysteme

unterschieden. Aufgrund der Datenstruktur wurde für die Auswertung der Mortalität und der

Verhaltensmerkmale die Legelinie LIN(SYS) nicht mit in das Modell einbezogen. Für die

Verhaltensmerkmale waren Legelinie und Ort der Untersuchung miteinander verknüpft. Für

das Merkmal Legeleistung wurde aufgrund der Datenstruktur der ORT(SYS) nicht in das

Modell aufgenommen.

Yijkl = µ + SYSi + ORT(SYS)ij + LIN(SYS)ik + eijkl

Yijkl LSM für die Merkmale Humerus- und Tibiabruchfestigkeit (jeweils n =

36), Brustbeinstatus (n = 24), Fußballenstatus (n = 21), Gefiederstatus

(n = 21), Legeleistung pro Bestandshenne (n = 30), Mortalität (n = 36),

Eischalenbruchfestigkeit (n = 24) sowie für die Verhaltensmerkmale (n

= 14)

μ Modellkonstante

eijkl zufälliger Restfehler

3 Ergebnisse

Die Ergebnisse der Varianzanalyse zeigten, dass der fixe Effekt des Haltungssystems einen

signifikanten Einfluss auf die Merkmale Humerus- und Tibiabruchfestigkeit,

Sohlenhyperkeratose, Legeleistung, Mortalität und Sandbaden auf dem Drahtboden hatte

(Tab. 2), während er sich für die Merkmale Brustbeinstatus, Epithelläsion der Sohle,

Gefiederstatus, Eischalenfestigkeit sowie für die übrigen ausgewählten Verhaltensmerkmale

als nicht signifikant erwies. Ein signifikanter Einfluss des Untersuchungsortes wurde für die

Merkmale Tibiabruchfestigkeit, Gefiederstatus, Mortalität, Picken im Sandbad, Federpicken,

Aufenthalt auf den Sitzstangen (Stehen/Sitzen) und Sandbaden auf dem Boden festgestellt.

Der fixe Effekt der Legelinie erwies sich ausschließlich für die Legeleistung als signifikant.

Hennen in konventioneller Käfighaltung wiesen im Vergleich zu allen übrigen

Haltungssystemen eine geringere Humerus- und Tibiabruchfestigkeit auf. Weiterhin zeigten

Hennen aus beiden Varianten des ausgestalteten Käfigs und der Kleingruppenhaltung eine

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geringere Humerus- und Tibiafestigkeit im Vergleich zur Volierenhaltung, mit Ausnahme der

in EV 625A-EU gehaltenen Hennen, welche eine mit der Volierenhaltung vergleichbare

Tibiafestigkeit und somit auch eine signifikant günstigere Tibiafestigkeit als Hennen im

ausgestalteten Käfig Aviplus und in der Kleingruppenhaltung aufwiesen. Die

Humerusfestigkeit von Hennen aus Kleingruppenhaltung und ausgestalteten Käfigen

unterschied sich nicht signifikant voneinander.

Hennen aus dem Aviplus (AP) zeigten eine geringere Humerus- und Tibiafestigkeit

verglichen mit Tieren aus der intensiven Auslaufhaltung. Zwischen den beiden untersuchten

EV Systemen und der intensiven Auslaufhaltung konnten keine Unterschiede in der

Humerusfestigkeit beobachtet werden. Für Hennen aus Kleingruppenhaltung zeigte sich im

Vergleich zur intensiven Auslaufhaltung eine niedrigere Tibiafestigkeit.

Hennen im EV 625a-EU zeigten vermehrt hyperkeratotische Veränderungen an den Sohlen

im Vergleich zu Hennen aus AP, während sich die übrigen Haltungssysteme in diesem

Merkmal nicht voneinander unterschieden.

Die Legeleistung der Hennen aus konventioneller Haltung unterschied sich nicht von Tieren

aus den übrigen Haltungssystemen. Hennen aus AP, EV 625A-EU und EV 625a-EU erzielten

eine höhere Legeleistung im Vergleich zur Volieren- und intensiven Auslaufhaltung. Darüber

hinaus zeigten Hennen aus EV 625A-EU eine höhere Legeleistung als Tiere aus AP und EV

625a-EU. Hennen aus der Volierenhaltung zeigten die höchste Mortalitätsrate und die

Unterschiede zu den Systemen AP, EV 625A und EV 625a-EU erwiesen sich als signifikant.

Keine Unterschiede in der Mortalitätsrate zeigte sich zwischen Hennen aus Volierenhaltung,

intensiver Auslaufhaltung und konventioneller Käfighaltung.

Hennen aus AP zeigten signifikant häufigeres Sandbadeverhalten auf dem Drahtboden im

Vergleich zu Hennen aus EV 625a-EU und EV 625A-EU, während Hennen aus den beiden

letztgenannten Systemen sich in diesem Merkmal nicht voneinander unterschieden.

Obwohl der fixe Effekt des Haltungssystems für den Brustbein- und Gefiederstatus sowie für

das Merkmal Aufenthalt auf den Sitzstangen (Stehen/Sitzen) nicht signifikant war, zeigten

sich bei einzelnen Vergleichen der Systeme signifikante Unterschiede. So wiesen Hennen aus

Volierenhaltung einen ungünstigeren Brustbeinstatus im Vergleich zu EV 625a-EU auf,

unterschieden sich jedoch nicht von Hennen aus EV 625A-EU und AP. Weiterhin wurde bei

Hennen aus der Volierenhaltung ein signifikant günstigerer Gefiederstatus verglichen mit

Tieren aus ausgestalteten Käfigen und Kleingruppenhaltung beobachtet. Hinsichtlich der

Verhaltensmerkmale hielten sich im AP signifikant mehr Hennen auf den Sitzstangen auf

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(Stehen, Sitzen) als Hennen aus EV 625A-EU, während Hennen aus EV 625a-EU die

Sitzstangen signifikant häufiger zum Stehen und Sitzen nutzten als Hennen aus EV 625A-EU.

4 Diskussion

Die Meta-Analyse erbrachte in mehrerer Hinsicht bemerkenswerte Ergebnisse. Nur wenige

Merkmale zeigten signifikante Unterschiede zwischen den sechs untersuchten

Haltungssystemen. Im Haltungssystem EV 625A-EU war die Mortalität am geringsten, die

Legeleistung pro Bestandshenne und damit auch pro Anfangshenne am höchsten und die

Gesundheitsmerkmale am ausgewogensten. Die Hyperkeratosen der Sohle waren niedrig und

der Brustbeinstatus zeigte keinen Unterschied im Vergleich zu den anderen untersuchten

Haltungsformen. Die Tibiaknochenfestigkeit war mit den in der Voliere gemessenen Werten

vergleichbar und sowohl Humerus- als auch Tibiafestigkeit unterschieden sich nicht von

Werten aus der intensiven Auslaufhaltung. Im Vergleich zur konventionellen Käfighaltung

wurde in allen untersuchten Haltungssystemen eine bessere Humerus- und

Tibiaknochenfestigkeit erzielt. Die in dieser Untersuchung festgestellte Verbesserung der

Humerus- und Tibiafestigkeiten von Hennen aus ausgestalteten Käfigen und

Kleingruppenhaltungen im Vergleich zur konventionellen Käfighaltung kann neben der

Sitzstangennutzung auch durch den sogenannten „Omnibuseffekt“ hervorgerufen worden

sein, der den Hennen das Zurücklegen größerer Distanzen (insbesondere in der

Kleingruppenhaltung) innerhalb eines Abteils ermöglichte und sich somit in erster Linie

positiv auf die Tibiafestigkeit ausgewirkt haben könnte. Ebenfalls kann eine Aufteilung der

Haltungseinheiten in Sandbad-, Sitzstangen- und Nestbereich und eine hohe Akzeptanz der

verschiedenen Bereiche, dazu beigetragen haben, dass die Hennen angeregt wurden, sich

zwischen den genannten Arealen zu bewegen. Die in der Volierenhaltung erzielten hohen

Knochenfestigkeiten konnten jedoch nicht für Legehennen im Aviplus System und in der

Kleingruppenhaltung ermittelt werden und wurden auch nicht durch die intensive

Auslaufhaltung übertroffen. Das Nutzen des Etagenelementes und des angegliederten

Kaltscharrraumes bot den Hennen in der Voliere eine Vielzahl an Bewegungsmöglichkeiten,

welche sich positiv auf eine Erhöhung der Knochenfestigkeit ausgewirkt hat. Die im EV

625A-EU ermittelte und mit der Volierenhaltung vergleichbare Tibiafestigkeit lässt sich in

diesem Zusammenhang schwer erklären. Da im Gegensatz zum Aviplus System die

Sitzstangen im EV 625A-EU teilweise auf verschiedenen Ebenen installiert waren, könnte

sich dies sehr positiv auf die Tibiafestigkeit in diesem System ausgewirkt haben. In einer

Untersuchung von BISHOP et al. (2000) wurde eine positive Korrelation zwischen Humerus-

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und Tibiafestigkeit sowie dem Brustbeinstatus beschrieben. Trotz hoher Humerus- und

Tibiaknochenfestigkeit in der Volierenhaltung wurde in diesem System jedoch ein

ungünstiger Brustbeinstatus im Vergleich zur Kleingruppenhaltung beobachtet. In einer

umfassenden Studie von ELSON und CROXALL (2006) wurde ebenfalls ein verminderter

Brustbeinstatus bei Hennen in Volieren festgestellt. GREGORY et al. (1990) beschrieben als

einen prädisponierenden Faktor für Brustbeinveränderungen ein hohes Kollisionsrisiko durch

fehlerhaftes Anfliegen von Sitzstangen bei Hennen in Volierenhaltung. Ursache für ein

vermehrtes Unfallrisiko könnte eine ungünstige Sitzstangenpositionierung sein. Laut einer

Studie von MOINARD et al. (2004) sollten Sitzstangen einen Abstand von 600 mm nicht

überschreiten, um den Hennen eine problemlose Nutzung zu gewährleisten. Die in der Voliere

installierten Sitzstangen hatten einen Abstand von 830 mm zum Boden und 480 bzw. 740 mm

Abstand zu der obersten Etage des Volierenelementes. Dies könnte möglicherweise mit einem

höheren Kollisionsrisiko assoziiert gewesen sein. BESSEI (1997) wies ebenfalls darauf hin,

dass Anflugsitzstangen optimal positioniert sein müssen, um das Risiko von Frakturen zu

minimieren. Obwohl der Brustbeinstatus in den ausgestalteten Käfigen sich nicht von den

Werten der Volierenhaltung unterschied, war zwischen letzterem System und der

Kleingruppenhaltung ein signifikanter Unterschied zu verzeichnen. KEELING et al. (2003)

stellten bei Hennen in Abteilen mit Gruppengrößen um die 30 Hennen eine vermehrte Unruhe

aufgrund einer instabilen sozialen Hierarchie fest. In diesem Zusammenhang könnten die

teilweise auf verschiedenen Ebenen positionierten Sitzstangen in den 30-er Abteilen des EV

625A-EU vermehrt zu ungewollten Kollisionen mit dem Brustbein geführt haben, während in

den größeren Gruppen der Kleingruppenhaltung eine tolerantes Sozialverhalten auftrat, dass

mit weniger Unruhe verbunden war. In einer Studie von WAHLSTRÖM et al. (2001) wurden die

in ausgestalteten Käfigen beschriebenen Brustbeinveränderungen auf starke mechanische

Belastung bei der Sitzstangennutzung zurückgeführt. In der vorliegenden Studie führte nur die

Nutzung der Sitzstangen in der Kleingruppenhaltung weniger stark zu Deformationen des

Brustbeins als die Haltungsbedingungen im untersuchten Volierensystem. GENTLE (2001)

konnte in einer Studie eindeutige Hinweise auf komplexe Vorgänge der

Schmerzwahrnehmung bei Geflügel nachweisen, so dass die in der Voliere auftretenden

Brustbeindeformationen durchaus kritisch zu bewerten sind.

Legehennen im den untersuchten Kleingruppenhaltungssystemen waren stärker von

hyperkeratotischen Veränderungen der Sohlenballen betroffen. Hierzu könnte eine

unterschiedlich frequente Nutzung der Sitzstangen beigetragen haben. Darüber hinaus wird

der Fußballenstatus durch das Design der angebotenen Sitzstangen maßgeblich beeinflusst

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(SIEGWART, 1991; OESTER, 1994; TAUSON und ABRAHAMSSON, 1994). Form und

Oberflächenbeschaffenheit der in der Kleingruppenhaltung installierten Sitzgelegenheiten

unterschieden sich teilweise von denen der ausgestalteten Käfige. In allen untersuchten LD

war den Hennen im Kleingruppenhaltungssystem das Nutzen des Zuleitungsrohres der

Sandbadbefüllung als Sitzgelegenheit möglich. Durch seine runde Form und die

vergleichsweise raue Oberfläche, könnte eine vermehrte Proliferation der Sohlenballenhaut

hervorgerufen worden sein (WEITZENBÜRGER et al, 2005). In Studien von SIEGWART (1991)

und WEITZENBÜRGER et al. (2005) werden als Ursache des Entstehens von

Sohlenballenhyperkeratose vor allem die Nutzung von Sitzstangen angesehen. Läsionen und

Entzündungen werden am häufigsten in alternativen Haltungssystemen beobachtet (KEUTGEN

et al., 1999). So begünstigt eine feuchte und durch Exkremente verunreinigte Einstreu (WANG

et al., 1998) sowie mangelnde Sauberkeit von Sitzstangen (ELSON und CROXALL, 2006)

entzündliche Veränderungen der Fußballen. Entgegen Blokhuis et al. (2007) konnte in der

vorliegenden Studie jedoch kein vermehrtes Auftreten von Sohlenballenläsionen in der

Volierenhaltung im Vergleich zu den ausgestalteten Käfigen und Kleingruppenhaltungen

beobachtet werden. Dies könnte auf guten hygienischen Zustand des verwendeten

Einstreumaterials zurückgeführt werden.

Ein intaktes Gefieder trägt maßgeblich zum Wohlbefinden der Hennen bei. Gefiederschäden

können sowohl durch Einrichtungselemente in Käfighaltungssystemen (FREIRE et al., 1999)

als auch durch einen gegenseitigen Abrieb zwischen Hennen bei hoher Besatzdichte

verursacht werden (APPLEBY et al., 2002). Diese Faktoren könnten den in den ausgestalteten

Käfigen und Kleingruppenhaltungen beobachteten ungünstigeren Gesamtgefiederstatus der

Hennen im Vergleich zur Volierenhaltung hervorgerufen haben. Federpicken stellt ebenfalls

eine wichtige Ursache für das Auftreten von Gefiederschäden dar (BILČÍK und KEELING,

1999). Die durchgeführten Untersuchungen zum Verhalten zeigten jedoch keine Unterschiede

hinsichtlich des Auftretens von Federpicken in Kleingruppenhaltung und den ausgestalteten

Käfigen. Verhaltensbeobachtungen in der vorliegenden Studie umfassten die Untersuchung

von Merkmalen, die Rückschlüsse auf die Raumnutzung sowie Akzeptanz der

Einrichtungselemente der Haltungseinheiten zuließen. Obwohl die Kleingruppenhaltung

aufgrund der größeren Grundfläche der Abteile Möglichkeit zu mehr Fortbewegung bot,

konnte kein Unterschied in der Häufigkeit der Fortbewegung (Gehen auf Drahtboden) zum

ausgestalteten Käfig ermittelt werden. Ebenso konnten keine Abweichungen zwischen den

Haltungssystemen für die Merkmale Ruhen auf den Sitzstangen und Aufenthalt (Stehen) auf

dem Drahtgitterboden ermittelt werden. Hennen aus EV 625a-EU nutzten Sitzstangen im

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Vergleich zum EV 625A-EU zum Sitzen/Stehen vermutlich häufiger, da ihnen durch das

Zuleitungsrohr zur Sandbadbefüllung eine zusätzliche Möglichkeit der Sitzstangennutzung

zur Verfügung stand. Sandbaden stellt ein wichtiges Element des Komfortverhaltens dar. In

neuartigen Haltungssystemen, in denen durch Ausgestaltung der Abteile mit

Sandbadevorrichtungen den Legehennen die Ausübung des Sandbadens ermöglicht wird, ist

dieser Bereich jedoch noch immer als eine Schwachstelle anzusehen (BUCHENAUER, 2005).

So kritisierten WEITZENBÜRGER et al. (2006b) unter anderem die Größe der angebotenen

Staubbäder, die das von Hennen bevorzugte Sandbaden in der Gruppe nur eingeschränkt

zuließ. In der vorliegenden Studie wurde Sandbadeaktivität auf dem Drahtboden signifikant

häufiger im AP beobachtet im Vergleich zur Kleingruppenhaltung und EV 625A-EU. Dies

könnte möglicherweise auf ungünstigere Lichtverhältnisse in den Sandbadevorrichtungen des

AP zurückgeführt werden. Aufgrund der zentralen, lichtundurchlässigen Trennwand war die

Lichtintensität in diesen Bereichen im Vergleich zur Kleingruppenhaltung (ohne Trennwand)

und dem EV 625A-EU (Trennwand zur Hälfte aus Gitterdraht) geringer. BUCHENAUER (2005)

konnte das Ausüben des Sandbadeverhaltens oftmals auf dem Drahtboden in Nähe einer

Lichtquelle beobachten, da die Sandbadevorrichtungen nicht genügend ausgeleuchtet waren

und somit der wichtige Schlüsselreiz des Lichtes fehlte. Auch die im Vergleich zu EV 625a

und EV 625A zeitlich limitierte Verfügbarkeit des Sandbads im AP wird als Grund einer

erhöhten Sandbadeaktivität auf dem Drahtboden angesehen, da die Hennen nur unzureichend

Möglichkeiten hatten, ihr Sandbadeverhalten während des begrenzten Zugangs zu der

Sandbadevorrichtung auszuüben. Pickaktivitäten werden zum Funktionskreis des

Erkundungs- und Nahrungsaufnahmeverhaltens gezählt. WEITZENBÜRGER et al. (2006b)

erwähnten einen möglichen Zusammenhang zwischen einem gehäuften Auftreten von

Federpicken und gleichzeitig verminderter Pickaktivität im Sandbad in ausgestalteten Käfigen

und führten dies auf einen Mangel an adäquatem Erkundungs- und Beschäftigungsmaterials

zurück, welches die Hennen veranlasste, Pickaktivitäten auf das Gefieder ihrer Artgenossen

zu projizieren. In der vorliegenden Studie konnten für die Verhaltensmerkmale Federpicken,

Pickaktivität im Sandbad sowie gegen Objekte gerichtetes Picken keine Unterschiede

zwischen ausgestalteten Käfigen und der Kleingruppenhaltung beobachtet werden. Da alle

aufgeführten Pickaktivitäten in den untersuchten Systemen beobachtet wurden, konnte aus

den vorliegenden Ergebnissen nicht geschlussfolgert werden, ob Menge und Struktur des

angebotenen Scharrmaterials geeignet waren, den Erkundungstrieb der Tiere voll zu

befriedigen. Die in der Volieren- und Auslaufhaltung niedrigere Legeleistung im Vergleich zu

ausgestaltetem Käfig und Kleingruppenhaltung entspricht den Ergebnissen von BLOKHUIS et

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al. (2007). Nicht vollständig geschlossene Haltungssysteme bergen aufgrund externer

Umwelteinflüsse ein größeres Gesundheitsrisiko für Hennen, welches zusammen mit oftmals

höherem Futteraufwand zu einer größeren, wirtschaftlichen Unsicherheit des Haltungssystems

führen kann. Die in der Volierenhaltung im Vergleich zu ausgestaltetem Käfig und

Kleingruppenhaltung aufgetretene höhere Mortalitätsrate spiegelt diesen Aspekt ebenfalls

wider.

Schlussfolgernd lässt sich sagen, dass sich die technische Weiterentwicklung der

Legehennenhaltungssysteme hin zu ausgestalteten Käfigen und Kleingruppen positiv auf die

erfassten gesundheits- und leistungsbezogenen Merkmale im Vergleich zur konventionellen

Käfighaltung ausgewirkt hat. Die Volierenhaltung konnte in den Merkmalen Humerus- und

Tibiaknochenfestigkeit nicht übertroffen werden, wobei Hennen aus EV 625A-EU eine

vergleichbare Tibiafestigkeit aufwiesen. Hennen aus der Voliere zeichneten sich durch einen

ungünstigeren Brustbeinstatus im Vergleich zur Kleingruppenhaltung aus und wiesen eine

höhere Mortalität und geringere Legeleistung auf. Die Weiterentwicklung der ausgestalteten

Käfige zur Kleingruppenhaltung brachte weitere Verbesserungen in den untersuchten

Gesundheits-, Leistungs- und Verhaltensmerkmalen. Hinsichtlich wirtschaftlicher Aspekte

(Legeleistung, Mortalität) boten ausgestaltete Käfige und Kleingruppenhaltungssysteme

deutliche Vorteile gegenüber der Volierenhaltung. In den untersuchten ausgestalteten Käfigen

sind gegenüber den anderen alternativen Haltungsformen bestimmte Verhaltensweisen stark

eingeschränkt beziehungsweise fehlgeleitet (Sandbadeverhalten auf dem Drahtboden im AP),

so dass auch unter Verhaltensaspekten eine Weiterentwicklung der ausgestalteten Käfige zur

Kleingruppenhaltung notwendig war.

Zusammenfassung

In der vorliegenden Studie wurden mittels Meta-Analyse gesundheits- und leistungsbezogene

Parameter, sowie ausgewählte Verhaltensmerkmale von Legehennen in unterschiedlichen

Haltungssystemen untersucht. Einbezogen wurden eigene Untersuchungsergebnisse sowie

bereits veröffentlichte Daten verschiedener Autoren zu insgesamt zehn Legedurchgängen und

einer Gesamtzahl von 4.553 Hennen. Die getesteten Haltungssysteme waren konventionelle

Käfige, zwei Varianten eines ausgestalteten Käfigs, Kleingruppenhaltungen, ein

Volierensystem, sowie eine intensive Auslaufhaltung. Die Analyse umfasste die LS-

Mittelwerte (LSM) von Humerus- und Tibiaknochenfestigkeit, Brustbein-, Fußballen- und

Gefiederstatus, Legeleistung, Mortalität, Eischalenfestigkeit sowie Verhaltensmerkmale der

Hennen. Die LSM der einbezogenen Studien wurden anhand der Reziprokwerte ihrer

109


quadrierten Standardfehler gewichtet und die Meta-Analyse erfolgte anhand eines linearen

Weighted Least Square Modells. Das Haltungssystem erwies sich für Humerus- und

Tibiabruchfestigkeit, Sohlenballenhyperkeratose, Legeleistung, Mortalität und Sandbaden auf

dem Drahtboden als signifikant. Im Vergleich zu den ausgestalteten Käfigen und der

Kleingruppenhaltung erzielten die in der Voliere gehaltenen Hennen die höchsten

Knochenfestigkeiten, zeigten jedoch einen ungünstigeren Brustbeinstatus verglichen mit den

ausgestalteten Käfigen, sowie eine geringere Legeleistung und höhere Mortalität.

Hyperkeratotische Veränderungen der Sohlenballen traten am häufigsten in der

Kleingruppenhaltung auf. Für die Merkmale Humerusbruchfestigkeit, Brustbein- und

Gefiederstatus, Eischalenfestigkeit, Mortalität sowie für die ausgewählten

Verhaltensmerkmale, mit Ausnahme der Sandbadeaktivität auf dem Drahtboden und des

Aufenthaltes auf den Sitzstangen (Stehen und Sitzen), konnten keine Unterschiede zwischen

ausgestaltetem Käfig und Kleingruppenhaltung festgestellt werden.

Schlüsselwörter: Meta-Analyse, Legehennen, Gesundheitszustand, Verhalten,

Haltungssysteme

110


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Danksagung

Die Autoren danken der Big Dutchman GmbH, der Lohmann Tierzucht GmbH und der

Deutschen Frühstücksei GmbH für die finanzielle Unterstützung des Forschungsprojektes.

Meta-analysis of welfare, egg quality, production and selected behavioural traits to

evaluate small group housing systems for laying hens

Abstract

The objective of the current investigation was to employ the tool of meta-analysis in order to

assess selected welfare, behavioural and production traits of four different layer strains kept in

different types of housing systems. The study was carried out from 1999 to 2006 at two

experimental farms and included data of ten laying periods, comprising 4,553 hens in total.

Data was collected by the different authors employing fully identical methods. Housing

systems tested were conventional cages, two types of furnished cages, small group systems,

an aviary housing system and an intensive free range system. Least square means (LSM) of

the traits bone strength, keel bone status, foot pad health, plumage condition, egg shell

strength, production, mortality and selected behavioural patterns were chosen for meta-

analysis. LSM given by the included studies were weighted with their squared, reciprocal

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standard errors and meta-analysis was carried out using a linear Weighted Least Square

Model. Housing system had a significant effect on humerus and tibia bone strength,

hyperkeratosis of sole pad, production, mortality rate and dustbathing on wire floor. At the

expense of inferior keel bone status compared to furnished cages and unfavourable production

and mortality rate, bone strength of hens kept in the aviary system could not be exceeded by

any other type of housing system tested. Foot pad health of hens kept in the aviary was not

found to be unfavourable although litter had been provided and hyperkeratosis of sole pad

was found to be mostly prevalent in the small group systems. Highest production and lowest

mortality rates were detected in furnished cages and small group systems. Humerus bone

strength, keel bone status, plumage condition, eggshell strength, mortality rate and the

selected behavioural patterns, except the traits dust bathing on wire floor and standing/sitting

on perch, did not differ between hens kept in furnished cages and small group systems.

Key words: meta-analysis, laying hen, welfare, behaviour, housing system

114


Tab. 1. In die Meta-Analyse einbezogene Studien, deren Untersuchungszeiträume (LD),

Versuchsfarmen, Haltungssysteme, verwendete Legelinien (LIN), Anzahl untersuchter

Hennen (n) und Anfangsbestand (AB) der jeweils in dem Versuchsstall eingestallten Hennen.

Studies included in the meta-analysis, their investigation periods (LD), trial farms, housing

systems, layer lines (LIN), number of hens (n) examined and total number of hens housed.

LuFG Ruthe VS Wesselkamp LD

Studien, Systeme LIN n AB Studien, Systeme LIN n

AB

1999-2000

Leyendecker et al. (2001a, 2001b)

KK, Voliere, AH

LSLLT

300 4.500 - - -

2000-2001

Leyendecker et al. (2005)

KK, AP, Voliere LS 600

5.211 - - -

2001-2002

Leyendecker et al. (2005)

KK, AP, Voliere LS 675

4.882 - - -

2002-2003

Leyendecker, unveröffentlicht LS 628

5.410

Vits et al. (2005), Weitzenbürger et al. (2005, 2006a, 2006b)

AP, EV 625A-EU, EV 625a-EU

LB LSL

432 8.640

2003-2004 - - -

Vits et al. (2005), Weitzenbürger et al. (2005, 2006a, 2006b)

AP, EV 625A-EU, EV 625a-EU LSL 432

8.640

2004-2005

Scholz et al. (2006) Rönchen et al. (2006),*

AP, EV 625aEU, Voliere

LS LT

478 5.490

Scholz/Rönchen* AP, EV 625A-EU, EV 625a-EU

LB LSL

288 ca.

9.000

2005-2006

Scholz/Rönchen* AP, EV 625a-EU,

Voliere LS 432

5.560Scholz/Rönchen*

AP, EV 625A-EU, EV 625a-EU LSL 288 ca.

9.000 KK: konventioneller Käfig; AP: AP; AH: intensive Auslaufhaltung; EV: Eurovent; LD:

Legedurchgang; LIN: Legelinie; LSL: Lohmann Selected Leghorn, LT: Lohmann Tradition;

LS: Lohmann Silver; LB: Lohmann Brown; *: zur Veröffentlichung eingereicht

115


116

Tab. 2. Signifikante Unterschiede der Meta-Analyse zwischen den verschiedenen Haltungssystemen

bezogen auf die Merkmale Humerus- und Tibiabruchfestigkeit, Hyperkeratose der Sohle (HypS),

Legeleistung pro Bestandshenne (LL), Mortalitätsrate (Mort) und Sandbadeaktivität auf dem

Drahtboden (Sb Draht)

Significant differences of meta-analysis among the different housing systems tested related to the

traits humerus- and tibia bone strength, sole pad hyperkeratosis (HypS), production rate per hen

present (LL), mortality rate (Mort) and dustbathing on wire floor (Sb Draht)

Humerus (N)

Tibia (N)

HypS (1-5)

LL (%)

Mort (%)

Sb Draht (%) Sys

LSM SE LSM SE LSM SE LSM SE LSM CIu CIo LSM SE

KK 107,98a 15,74 107,34a 4,45 - - 81,20abcd22,69 11,1ab 0,07 0,16 - - AP 169,83b 8,09 129,98b 1,98 1,83a 0,04 87,57a 0,22 5,86c 0,04 0,08 0,96a 0,07EVA 195,23bc 12,81 143,44c 3,53 1,88ab 0,08 88,75b 0,15 3,74c 0,02 0,06 0,61b 0,09EVa 184,42bc 9,72 133,67b 2,23 2,04b 0,04 87,88a 0,22 5,51ac 0,03 0,09 0,52b 0,06VOL 237,14d 14,85 153,26c 3,95 2,02ab 0,12 79,50c 0,60 12,23b 0,09 0,16 - - AH 231,90cd 23,10 153,25c 6,52 - - 74,21d 0,85 9,68abc 0,04 0,21 - - Sys: Haltungssystem; KK: konventioneller Käfig; AP: AP; EVA: EV 625A-EU; EVa: EV 625a-EU;

VOL: Voliere; AH: intensive Auslaufhaltung; verschiedene Buchstaben (a, b, c, d) innerhalb einer

Spalte kennzeichnen signifikante Differenzen (p < 0,05) zwischen den Haltungssystemen für das

jeweilige Merkmal

Chapter VIII

Summary

Chapter VIII: Summary

Summary

by Britta Scholz (2007)

Evaluation of small group systems with elevated perches, furnished cages and an aviary

system for laying hens with respect to bone strength, keel bone status, stress perception

and egg quality parameters.

The objective of the present investigation was to assess different kinds of house keeping

systems for laying hens with respect to humerus and tibia bone breaking strength,

macroscopic and histological keel bone condition, layers’ stress exposure and selected

internal and external egg quality traits. Special focus was put on the only currently approved

small group system with elevated perch positions and the influence of the different perch

configurations and group sizes on laying hens’ welfare and production traits.

Small group systems with non-elevated perches could increase humerus and tibia bone

strengths in LS layers compared to hens housed in furnished cages, whereas bone strength of

LT layers was not positively affected. The aviary system showed a decisive impact on bone

characteristics of LS and LT hybrids. Bone strength was significantly increased, whereas keel

bone status tended to be inferior. For both layer lines, egg shell breaking strength was lower

in the small group system compared to furnished cages and aviary system. A favourable

predisposition of stronger bones, particularly related to LS layers, might have led to

preferential use of calcium for bone remodelling processes at the expense of calcium

provision for egg shell formation.

The small group system with elevated perches did not lead to increased humerus strength in

LS layers in comparison to the furnished cage system, whereas tibia strength was positively

influenced towards the end of the laying period. In addition, hens kept in small group

compartments with perches incorporated in the stepped position showed significantly higher

tibia bone strength compared to furnished cages. With relation to the different group sizes,

increased humerus strength was found in groups of 40 layers compared to groups of 60 hens.

Hens kept in the modified small group system showed an unfavourable keel bone status

compared to layers housed in furnished cages, thus suggesting a negative impact of elevated

perches on layers’ keel bone. However, a lower H/L-ratio in LS hens kept in the small group

system with modified perches suggested a lower stress exposition in comparison to hens kept

in the furnished cage system. The number of dirty and broken eggs recorded in the modified

118

Chapter VIII: Summary

119

small group system was significantly higher compared to furnished cages and aviary system.

Egg accumulation in front of nest boxes due to a high number of hens per nest box and risk of

laying eggs from elevated perches could have been responsible for the high number of

downgraded eggs.

In LSL layers, which are of a lighter body weight, elevated perches did succeed in increasing

humerus and tibia bone strengths in comparison to hens kept in furnished cages. Furthermore,

hens kept in compartments with either the back or front perches incorporated in an elevated

position showed higher humerus bone breaking strength compared to layers housed in

compartments with perches being installed in the stepped position. In LSL layers, perches

incorporated at different heights also led to an unfavourable keel bone condition. Although

humerus and tibia bone strengths were positively correlated with keel bone condition,

improvements in bone strength of LSL layers kept in the small group system with elevated

perches could not prevent keel bone deformities, which might have been caused by accidental

perch collisions or mechanical pressure on keel bone due to extended perching activities.

Histological evaluation of macroscopically assessed keel bone showed that in almost all

samples of unaltered keel bones, no histological deviations were found, whereas in

moderately to severely deformed keel bones, the incidence of fracture callus material was the

predominant histological finding, suggesting a traumatic origin and pain experience. In 50.9

% of sligthly deformed keel bones, fracture callus material was observed, whereas non-

traumatic s-shaped deformities, presumably as a response of layers’ keel bone to mechanical

forces while perching activities, were found in 40.7 % of slightly altered keels. Therefore,

histological analysis was found to be a mandatory tool when evaluating slightly deformed

keel bones with respect to layers’ welfare.

The tool of meta-analysis was employed in order to jointly analyse and discuss selected

welfare, behavioural and production parameters of hens kept in different types of housing

systems over 10 laying periods. These results showed that the technical advancements in the

development of laying hen husbandry systems from conventional cages to furnished cages

and small group systems had a positive influence on a variety of the selected welfare and

production traits. In aviary systems, laying hens’ humerus and tibia bone strengths could not

be exceeded, whereas keel bone status and production parameters (egg production, mortality)

were inferior compared to hens housed in furnished cages and small group systems.

Behavioural traits of hens kept in furnished cages and small group systems are still limited

and advancements in the development of laying hen husbandry systems should concentrate on

constant improvements of environmental housing conditions.

Chapter IX

Erweiterte Zusammenfassung

Chapter IX: Erweiterte Zusammenfassung

122

Erweiterte Zusammenfassung

Britta Scholz

Evaluierung von Kleingruppenhaltungen mit modifizierten Sitzstangenpositionen,

ausgestalteten Käfigen und einer Volierenhaltung für Legehennen im Hinblick auf

Knochenfestigkeiten, Brustbeinstatus, Stressbelastung und Eiqualitätsparameter.

Ziel dieser Untersuchung war es, verschiedene Haltungssysteme für Legehennen hinsichtlich

ihres Einflusses auf Knochenfestigkeit, Brustbeinstatus, Stressbelastung und

Eiqualitätsparameter zu untersuchen und zu beurteilen. Im Zuge der geänderten rechtlichen

Rahmenbedingungen in der Legehennenhaltung wurden in dieser Untersuchung erstmalig

Abteile von Kleingruppenhaltungen derart modifiziert, dass sie in dem Punkt der

Sitzstangenanordnung der von der Bundesregierung beschlossenen sogenannten Kleinvoliere

entsprachen, welche spätestens ab 2020 die bis dahin im Einsatz befindlichen ausgestalteten

Käfige ersetzen soll. Die Studie wurde über zwei Legedurchgänge zeitgleich auf zwei

verschiedenen Betrieben durchgeführt (Legehennenstall des Lehr- und Forschungsgutes

(LuFG) Ruthe der Stiftung Tierärztliche Hochschule Hannover und Versuchsstall (VS)

Wesselkamp der deutschen Frühstücksei GmbH, Ankum, Landkreis Osnabrück). Insgesamt

wurden vier verschiedene Legelinien getestet. Im ersten Legedurchgang wurden auf dem

LuFG Ruthe zu gleichen Teilen Lohmann Silver (LS) und Lohmann Tradition (LT) Hybride

eingestallt. Im zweiten Versuchsdurchgang standen ausschließlich LS zur Verfügung. Auf

dem LuFG Ruthe wurden eine Kleingruppenhaltung (Eurovent (EV) 625a-EU,

Gruppengrößen 40 und 60 Hennen), ein ausgestalteter Käfig (Aviplus, Gruppengrößen 10, 20

und 30 Hennen) sowie eine Volierenhaltung („Natura“, zwei Großgruppen zu je 1.250 Tieren)

installiert. Die Abteile der Kleingruppenhaltung wurden im zweiten Legedurchgang derart in

ihrer Sitzstangenanordnung verändert, dass sie in diesem Punkt den rechtlichen

Anforderungen der Kleinvoliere entsprachen. Die im ersten Durchgang in den jeweiligen

Abteilen des EV 625a-EU auf einer Ebene installierten Sitzstangen wurden hierzu entweder

beide erhöht und in stufiger Position angebracht (Variante ST) bzw. es wurden nur die zur

Abteilmitte hin zeigenden, hinteren Sitzstangen erhöht (Variante HH). Im VS Wesselkamp

standen zwei ausgestaltete Käfige (Aviplus, Gruppengrößen 10, 20 Hennen und EV 625A-

EU, Abteilgrößen 20 und 30 Hennen) und eine Kleingruppenhaltung EV 625a-EU (Abteile

für 40 und 60 Hennen) zur Verfügung. Im Eurovent 625A-EU wurden in beiden


123

Legedurchgängen etwa 40 % der Abteile mit modifizierten Sitzstangen ausgestattet

(Varianten VH (vordere Sitzstangen erhöht) und Variante HH), während im EV 625a-EU

System im ersten Legedurchgang etwa 33 % der Abteile (Variante HH) und im zweiten

Legedurchgang alle Abteile mit modifizierten Sitzstangen eingerichtet wurden (Varianten ST,

HH und VH). Im ersten Legedurchgang wurden im VS Wesselkamp die Legelinien Lohmann

Selected Legehorn (LSL) und Lohmann Brown (LB) verwendet, im zweiten Legedurchgang

wurden ausschließlich LSL eingestallt. Die Untersuchungen wurden auf dem LuFG Ruthe im

3., 6., 9. und 12. Legemonat vorgenommen, im VS Wesselkamp im 6. und 12. Legemonat. Zu

diesem Zweck wurde jeweils eine bestimmte Anzahl von Legehennen unter gleichmäßiger

Berücksichtigung von Haltungssystem, Legelinie und Gruppengröße zufällig entnommen und

in der Klinik für Geflügel der Stiftung Tierärztliche Hochschule Hannover geschlachtet.

Untersuchungen zur Humerus- und Tibiaknochenfestigkeit wurden jeweils am Folgetag nach

Herauspräparieren der Knochen durchgeführt. Die Beurteilung des Brustbeinstatus erfolgte

sowohl adspektorisch und palpatorisch als auch histologisch an ausgewählten

Brustbeinbefunden. Untersuchungen zur Messung der Stressbelastung wurden nur auf dem

LuFG Ruthe im 2. Legedurchgang durchgeführt. Hierzu wurde den Hennen unmittelbar nach

Entnahme aus dem jeweiligen Haltungssystem venöses Blut entnommen und ein Blutausstrich

zur späteren mikroskopischen Beurteilung des Heterophilen/Lymphozyten (H/L)-Ratios

angefertigt. Untersuchungen zur Eiqualität erfolgten im Abstand von vier Wochen (LuFG

Ruthe) und im Abstand von acht Wochen (VS Wesselkamp).

Hinsichtlich der Knochenfestigkeit konnte auf dem LuFG Ruthe bei den LS Hybriden des

ersten Legedurchganges ein signifikanter Anstieg der Humerus- und Tibiabruchfestigkeit in

der Kleingruppenhaltung EV 625a-EU im Vergleich zum Aviplus gemessen werden. Die

Legelinie LT hingegen zeigte keine Unterschiede in der Knochenfestigkeit zwischen Hennen

aus Kleingruppenhaltung und dem ausgestalteten Käfig. Auffällig für beide Legelinien war

der signifikante Einfluss der Volierenhaltung auf die Humerus- und Tibiabruchfestigkeit.

Vergleichbare Knochenfestigkeiten zu den Tieren aus Volierenhaltung konnten weder im

Aviplus noch in der Kleingruppenhaltung nachgewiesen werden. Im EV 625a-EU konnte

weder für LS noch für LT Hennen ein Unterschied in der Knochenfestigkeit zwischen den

beiden untersuchten Gruppengrößen ermittelt werden, während die Legelinie LT im Aviplus

eine signifikant höhere Humerusbruchfestigkeit in der Gruppengröße 10 im Vergleich zu

Abteilen mit 20 und 30 Hennen aufwies. Der Brustbeinstatus der Hennen unterschied sich

nicht signifikant zwischen den untersuchten Haltungssystemen. Es konnte jedoch für jedes


124

System eine signifikante Verschlechterung des Brustbeinstatus vom 3. zum 12. Legemonat

beobachtet werden. Die Untersuchungen zeigten, dass die Legelinie LS sehr viel sensibler auf

das vergrößerte Raumangebot in der Kleingruppenhaltung reagierte und bei LS Hennen

dementsprechend eine signifikant höhere Humerus- und Tibiabruchfestigkeit im Vergleich

zum Aviplus erzielt werden konnte. Hennen in der Volierenhaltung zeigten die signifikant

höchsten Knochenbruchfestigkeiten und eine vermutlich allgemeine Stärkung des Skeletts

konnte dazu beitragen, dass der in der Voliere ermittelte Brustbeinstatus sich lediglich

tendenziell, jedoch nicht signifikant negativ von den beiden anderen untersuchten

Haltungssystemen abgrenzte. Hinsichtlich der Untersuchungen zur Eiqualität wurden bei

Hennen aus der Kleingruppenhaltung signifikant geringere Eischalenfestigkeiten im

Vergleich zum ausgestalteten Käfig und der Voliere ermittelt.

Ziel der Untersuchungen im zweiten Legedurchgang auf dem LuFG Ruthe war es, die zu

diesem Zeitpunkt erstmalig in der Praxis erprobte Kleingruppenhaltung mit zwei

verschiedenen Varianten der Sitzstangenmodifikation (modifizierte Kleingruppe)

vergleichend zum Aviplus und zur Volierenhaltung zu untersuchen. Die Ergebnisse dieser

Studie zeigten, dass bei Hennen aus der modifizierten Kleingruppe keine signifikant höhere

Humerusbruchfestigkeit im Vergleich zum ausgestalteten Käfig gemessen werden konnte,

während sich die Tibiabruchfestigkeit im 12. Legemonat signifikant positiv von Tieren aus

dem Aviplus abgrenzte. Analog zu den Ergebnissen des ersten Versuchsdurchganges

unterschied sich die Humerus- und Tibiabruchfestigkeit der Hennen aus der Voliere

signifikant von den beiden anderen untersuchten Haltungssystemen. Bei Hennen, die in der

modifizierten Kleingruppe in Abteilen mit 40 Tieren gehalten wurden, konnte ein

signifikanter Anstieg der Humerusfestigkeit im Vergleich zu Gruppen mit 60 Hennen

nachgewiesen werden. Bei den getesteten Sitzstangenvarianten zeigten sich innerhalb der

Kleingruppe keine Unterschiede in der Knochenfestigkeit. Hennen aus Abteilen mit der

Variante ST wiesen jedoch eine signifikant höhere Tibiabruchfestigkeit im Vergleich zum

ausgestalteten Käfig auf, was auf eine hohe Akzeptanz dieser Sitzstangenmodifikation

hindeutet. Im Gegensatz zum ersten Versuchsdurchgang, der eine Tendenz zu einem

ungünstigeren Brustbeinstatus bei den Tieren aus Volierenhaltung aufzeigte, wurde im

zweiten Legedurchgang bei Hennen aus der Voliere im Vergleich zu den beiden anderen

Haltungssystemen ein signifikant ungünstigerer Brustbeinstatus festgestellt. Darüber hinaus

erwies sich der Brustbeinstatus der Tiere aus der modifizierten Kleingruppe annähernd

signifikant ungünstiger (P = 0,08) im Vergleich zum ausgestalteten Käfig. Dies könnte


125

möglicherweise auf eine vermehrte Kollision des Brustbeins mit den auf verschiedenen

Ebenen installierten Sitzstangen zurückgeführt werden, sowie auf eine hohe mechanische

Belastung des Brustbeins während der Sitzstangennutzung. Weiterhin zeigte die

Sitzstangenmodifikation HH einen signifikant ungünstigeren Einfluss auf den Brustbeinstatus

im Vergleich zu Hennen aus dem Aviplus. In der Untersuchung wurde eine positive

Korrelation von Residuen der Tibiabruchfestigkeit und Residuen des Merkmals

Brustbeinstatus nachgewiesen, jedoch konnten weder die modifizierte Kleingruppe noch das

Volierenhaltungssystem das Brustbein in seiner Festigkeit derart stärken, dass es Kollisionen

mit Sitzstangen oder vermehrter Druckbelastung standhalten konnte. Für die Legelinie LS

konnten die erhöhten Sitzstangen in der Kleingruppe nicht dazu beitragen, die

Humerusbruchfestigkeit zu verbessern, während positive Ergebnisse auf die

Tibiabruchfestigkeit nachweisbar waren. Der Brustbeinstatus erwies sich insbesondere bei

Tieren aus Volierenhaltung als problematisch und in der modifizierten Kleingruppe zeigten

sich eindeutige Tendenzen hin zu einem ungünstigeren Brustbeinzustand im Vergleich zum

Aviplus. Hinsichtlich der Eiqualitätsuntersuchungen konnten zwischen den untersuchten

Haltungssystemen keine Unterschiede in der Schalenfestigkeit, -dicke- und dichte sowie im

Schalengewicht festgestellt werden. Auffällig war jedoch ein hoher Anteil von Knick-, Bruch-

und Schmutzeiern in der Kleingruppe im Vergleich zu den übrigen zwei Haltungssystemen.

Ursächlich wurde hier ein erhöhter Rückstau und damit Kollisionsgefahr der Eier vor den

Legenestern vermutet, bzw. ein eventuelles Legen der Eier von den erhöhten Sitzstangen.

Das Ziel der Untersuchungen im VS Wesselkamp war es, den Einfluss der

Sitzstangenanordnung und der unterschiedlichen Gruppengrößen auf die oben genannten

Parameter bei den Legelinien LB und LSL zu untersuchen. Bei den LSL Hybriden handelte es

sich um Weißleger, welche sich durch ein geringeres Körpergewicht im Vergleich zu den

übrigen Legelinien auszeichneten. Im ersten Legedurchgang konnte für beide Legelinien kein

signifikanter Unterschied in der Humerus- und Tibiabruchfestigkeit sowie im Brustbeinstatus

zwischen den untersuchten Haltungssystemen festgestellt werden. Die im zweiten

Legedurchgang in der Kleingruppenhaltung EV 625a-EU installierten, drei verschiedenen

Varianten der Sitzstangenerhöhung hingegen übten einen signifikant positiven Einfluss auf

die Humerus- und Tibiabruchfestigkeit aus. Die in der Kleingruppe gemessenen

Knochenfestigkeiten unterschieden sich signifikant von dem ausgestalteten Käfig Aviplus.

Darüber hinaus wiesen Hennen aus Abteilen mit den Sitzstangenvarianten HH und VH eine

signifikant höhere Humerusbruchfestigkeit im Vergleich zu der Variante ST aus, während die


126

Tibiabruchfestigkeit nicht durch unterschiedliche Sitzstangenanordnungen innerhalb der

Abteile beeinflusst wurde. Im System Eurovent 625A-EU, welches in den beiden

untersuchten Legedurchgängen eine identische Sitzstangenanordnung hatte, zeigten Hennen

im zweiten Versuchsdurchgang eine signifikant höhere Humerus- und Tibiafestigkeit im

Vergleich zum Aviplus, was die im ersten Durchgang beobachtete Tendenz verifizierte.

Die auf verschiedenen Ebenen installierten Sitzstangen im EV 625a-EU schienen analog zu

den Beobachtungen auf dem LuFG Ruthe einen ungünstigen Einfluss auf den Brustbeinstatus

der LSL Hennen zu haben. Hennen zeigten einen nahezu signifikant ungünstigeren

Brustbeinstatus (P = 0,058) im Vergleich zum EV 625A-EU, wenn alle Abteile des EV 625a-

EU mit Sitzstangen auf zwei verschiedenen Ebenen ausgestattet waren. Die Gruppengrößen

übten keinen entscheidenden Einfluss auf die Knochenfestigkeit und den Brustbeinstatus der

LSL Hennen aus.

Zusammenfassend lässt sich sagen, dass die Sitzstangenmodifikationen im EV 625a-EU die

Humerus- und Tibiaknochenfestigkeit bei LSL Hennen positiv beeinflusste, während für die

Gruppengröße kein entscheidender Einfluss auf die Knochenfestigkeit nachgewiesen werden

konnte. Insbesondere die Sitzstangenanordnungen HH und VH im EV 625a-EU erwiesen sich

gegenüber der Variante ST als vorteilhaft. Obwohl die Knochenfestigkeit und der

Brustbeinstatus positiv korreliert waren, konnte die positive Beeinflussung der

Knochenfestigkeit durch das EV 625a-EU System jedoch nicht dazu beitragen, das Brustbein

vor Veränderungen durch Kollisionen oder lang anhaltender mechanischer Druckbelastung

durch Sitzstangennutzung zu schützen. In der Untersuchung wurde ein negativer Einfluss der

Kleingruppenhaltung mit modifizierten Sitzstangenhöhen auf den Brustbeinstatus manifest.

In einer weiteren Untersuchung wurde erstmalig die Stressbelastung bei LS Hybriden in

Kleingruppen mit modifizierten Sitzstangenpositionen (EV 625a-EU), ausgestalteten Käfigen

und einer Volierenhaltung (LuFG Ruthe) anhand des H/L-Ratios vergleichend ermittelt. Die

Ergebnisse dieser Studie zeigten, dass die in ausgestalteten Käfigen gehaltenen Hennen einer

im Vergleich zur Kleingruppe signifikant höheren und im Vergleich zur Voliere annähernd

signifikant höheren (P = 0,075) Stressbelastung unterworfen waren. Zwischen Tieren aus

Volierenhaltung und Kleingruppe hingegen konnte kein Unterschied im H/L-Ratio festgestellt

werden. Hennen, die im EV 625a-EU in Abteilen von 40 Tieren verbunden mit Sitzstangen in

der HH Variante gehalten wurden, zeigten einen signifikant niedrigeren H/L-Ratio und somit

eine geringere Stressbelastung im Vergleich zu Hennen in Abteilen von 10, 20 und 30 Tieren

aus dem Aviplus und vergleichend zu Hennen aus Abteilen des EV 625a-EU mit Sitzstangen


127

in der ST Variante. Die Unterschiede in der Stressbelastung der Tiere aus den 40-er Abteilen

der Kleingruppe (Variante HH) zum Volierenhaltungssystem erreichten annähernd

Signifikanz (P = 0,054). Bei einer Erweiterung des angewandten statistischen Modells konnte

gezeigt werden, dass Hennen aus der Kleingruppe (Gruppengröße 40, Variante HH) gegen

Ende der Legeperiode einen signifikant niedrigeren H/L-Ratio aufwiesen als Tiere aus

Volierenhaltung. In allen drei Haltungssystemen wurde ein signifikanter Anstieg des H/L-

Ratios vom 3. zum 12. Legemonat festgestellt. Die Ergebnisse zeigten, dass Hennen in

Kleingruppen (Gruppengröße 40, Variante HH) insbesondere gegen Ende der Legeperiode im

Vergleich zu den beiden anderen untersuchten Haltungssystemen der geringsten

Stressbelastung unterworfen waren. Die im hinteren Bereich der Abteile erhöhten Sitzstangen

des EV 625a-EU schienen einen sehr positiven Einfluss auf eine ungestörte

Sitzstangennutzung auszuüben und konnten somit in Verbindung mit einer Gruppengröße von

40 Hennen durch die geringste Stressbelastung das Wohlbefinden der Tiere steigern.

Ergänzend zur makroskopischen Beurteilung des Brustbeinstatus wurde in einer weiteren

Studie eine histologische Untersuchung ausgewählter Brustbeinpräparate durchgeführt. Ziel

dieser Untersuchung war es, die in einer Vielzahl von Untersuchungen zum Brustbeinstatus

angewandte makroskopische Klassifizierung anhand einer Notenskala von 1 bis 4 (1 =

hochgradig verändert, 2 = mittelgradig verändert, 3 = geringgradig verändert, 4 = ohne

besonderen Befund) histologisch zu überprüfen. Für die Untersuchung wurden Brustbeine

von allen vier der in dieser Studie verwendeten Legelinien untersucht. Die Probenahme

erfolgte zufällig und richtete sich ausschließlich nach Art der makroskopischen Bewertung.

Die Ergebnisse der Studie zeigten, dass Brustbeine, die makroskopisch als unauffällig

beurteilt wurden in 97,9 % der Fälle auch in der histologischen Untersuchung keinen

besonderen Befund aufwiesen. Bei 2,1 % der Präparate konnten histologisch schmale

periostale Exostosen entlang der intakten Kompakta nachgewiesen werden. Diese wurden als

natürliche Reaktion des Knochengewebes auf vermehrte mechanische Belastung gedeutet, um

die Knochenstruktur zu stützen. Bei mittelgradig veränderten Brustbeinen wurde in insgesamt

80,0 % der Fälle eine umfangreiche Geflechtknochenbildung beobachtet. Davon konnte bei

37,5 % der Tiere zusätzlich eine eindeutige Dislokation der Frakturenden (Kompakta)

festgestellt werden. Eine Ausbildung von Geflechtknochen ist stets ein Indikator für eine

vorangegangene Knochenfraktur, welche mit Schmerzen für das betreffende Tier verbunden

ist. In 10,0 % der Fälle mittelgradig deformierter Brustbeine wurden schmale, periostale

Exostosen entlang der Kompakta nachgewiesen und in weiteren 10,0 % der Fälle war das


128

Brustbein histologisch unauffällig bzw. wies eine leichte s-förmige Verbiegung auf, jedoch

ohne Ausbildung von Frakturkallus. Bei makroskopisch hochgradig veränderten Brustbeinen

wurden histologisch ausschließlich Veränderungen an der Knochenstruktur festgestellt.

Geflechtknochenbildung wurde in 73,3 % der Fälle beobachtet und in weiteren 26,7 %

wurden zusätzlich deutlich sichtbare Dislokationen der Frakturenden beobachtet.

Geringgradig veränderte Brustbeine stellten sich bei der makroskopischen Beurteilung und

der anschließenden histologischen Befundung sehr uneinheitlich dar. Während in 40,7 % der

Fälle histologisch entweder keine Veränderung bzw. lediglich eine Verbiegung des

Brustbeins ohne eine Ausbildung von Geflechtknochengewebe beobachtet wurde, traten bei

40,7 % der untersuchten Präparate Geflechtknochenbildungen. In 10,2 % der Fälle wurde

neben der Ausbildung von Geflechtknochen zusätzlich eine deutlich sichtbare Dislokation der

Frakturenden gefunden. Bei 8 % der makroskopisch unveränderten Präparate konnten

schmale periostale Ektostosen entlang der intakten Kompakta nachgewiesen werden. Die

Ergebnisse dieser Studie zeigten, dass die histologische Befundung des Brustbeins die

makroskopische Beurteilung hinsichtlich der Noten 4, 2 und 1 sehr gut widerspiegelt.

Geringgradig veränderte Brustbeine zeigten zu etwa gleichen Teilen eine durch vermehrte

Druckbelastung bei der Sitzstangennutzung entstandene Adaption des Brustbeins, welche

vermutlich nicht mit Schmerzen für das betroffenen Tier verbunden war, beziehungsweise

eine traumatisch bedingte, und somit mit Schmerzen verbundene, Ausbildung von

Geflechtknochengewebe. Die makroskopische Beurteilung von geringgradig veränderten

Brustbeinen im Hinblick auf Wohlergehen und insbesondere Schmerzempfindung bei Hennen

wurde ohne begleitende histologische Untersuchung als unzureichend angesehen.

Aufgrund der Komplexität des Gesamtprojektes, wurden die zu erhebenden Daten zu Beginn

der Untersuchung auf zwei Dissertationen, die jeweils in kumulativer Form verfasst worden

sind, aufgeteilt. In der abschließenden Meta-Analyse und Diskussion ausgewählter

gesundheits-, verhaltens- und leistungsbezogener Parameter wurden die Daten beider

Dissertationen zusammen geführt. Darüber hinaus wurden bereits veröffentlichte Daten

früherer Autoren, deren Studien mit identischer Methodik ebenfalls auf dem LuFG Ruthe und

im VS Wesselkamp durchgeführt worden sind, in die Meta-Analyse einbezogen. Diese

umfasst somit eine Gesamtauswertung von insgesamt zehn untersuchten Legedurchgängen

innerhalb des Zeitraumes 1999-2006. Für die Meta-Analyse wurden die LS-Mittelwerte aus

jedem Legedurchgang pro Ort der Untersuchung, Haltungssystem und Legelinie für

Humerus- und Tibiaknochenfestigkeit, Brustbein-, Gefieder- und Fußballenstatus


129

(Sohlenballenhyperkeratose, Sohlenballenläsion), Legeleistung, Mortalität,

Eischalenfestigkeit sowie für bestimmte in ausgestaltetem Käfig und Kleingruppenhaltung

erfasste Verhaltensmerkmale der Hennen ausgewählt. Die untersuchten Haltungssysteme

waren konventionelle Käfige, zwei Varianten eines ausgestalteten Käfigs (Aviplus, EV 625A-

EU), Kleingruppenhaltungen (EV 625a-EU), ein Volierensystem (Voliere „Natura“), sowie

eine intensive Auslaufhaltung. Die Meta-Analyse erfolgte anhand eines linearen Weighted

Least Square Modells (Prozedur GLM von SAS, Option „weight“), wobei die Reziprokwerte

der zugehörigen quadrierten Standardfehler (SE) als Gewichtung verwandt wurden. Das

Haltungssystem, der Untersuchungsort innerhalb des Haltungssystems, sowie die Legelinie

wurden als fixe Effekte berücksichtigt. Das Haltungssystem übte einen signifikanten Einfluss

auf die Merkmale Humerus- und Tibiabruchfestigkeit, Sohlenballenhyperkeratose,

Legeleistung, Mortalität und Sandbaden auf dem Drahtboden aus, während für die Merkmale

Brustbeinstatus, Sohlenballenläsion, Gefiederstatus, Eischalenfestigkeit sowie für die übrigen,

ausgewählten Verhaltensparameter kein signifikanter Einfluß des Haltungssystems beobachtet

werden konnte. Hennen aus konventioneller Käfighaltung zeigten im Vergleich zu allen

übrigen Haltungssystemen eine geringere Humerus- und Tibiafestigkeit. Bei den in der

Voliere gehaltenen Hennen konnte eine höhere Humerus- und Tibiabruchfestigkeit im

Vergleich zu Hennen aus den beiden Varianten des ausgestalteten Käfigs und der

Kleingruppenhaltung nachgewiesen werden. Eine Ausnahme bildeten Hennen aus EV 625A-

EU, welche eine mit der Volierenhaltung vergleichbare Tibiafestigkeit aufwiesen und sich in

diesem Merkmal signifikant von Hennen aus Aviplus und der Kleingruppenhaltung

abgrenzten. Hennen aus Volierenhaltung zeichneten sich durch einen ungünstigeren

Brustbeinstatus im Vergleich zur Kleingruppenhaltung aus, sowie durch eine geringere

Legeleistung und höhere Mortalitätsrate. Hennen in der Kleingruppe wiesen vermehrt

hyperkeratotische Veränderungen am Sohlenballen im Vergleich zum Aviplus System auf,

während sich Hennen aus den übrigen Haltungsformen in diesem Merkmal nicht voneinander

unterschieden. Die höchste Legeleistung und die geringsten Mortalitätsraten wurden in den

beiden Varianten des ausgestalteten Käfigs und in der Kleingruppenhaltung erzielt. Die

Legeleistung der Hennen aus Volierenhaltung war geringer im Vergleich zu den

ausgestalteten Käfigen und der Kleingruppenhaltung, jedoch höher verglichen mit der

intensiven Auslaufhaltung. Die Ergebnisse der Meta-Analyse zeigten dass sich die technische

Weiterentwicklung der Legehennenhaltungssysteme von der konventionellen Käfighaltung

hin zu ausgestalteten Käfigen und Kleingruppen positiv auf die erfassten gesundheits- und

leistungsbezogenen Merkmale ausgewirkt hat. Die Volierenhaltung konnte in den Merkmalen


130

Humerus- und Tibiaknochenfestigkeit nicht übertroffen werden, wobei Hennen aus EV 625A-

EU eine vergleichbare Tibiafestigkeit aufweisen konnten. Gegenüber alternativen

Haltungsformen sind in den ausgestalteten Käfigen und Kleingruppensystemen bestimmte

Verhaltensweisen immer noch stark eingeschränkt beziehungsweise werden fehlgeleitet, wie

zum Beispiel das vermehrt bei Hennen im Aviplus beobachtete Sandbadeverhalten auf dem

Drahtboden, so dass eine stetige Weiterentwicklung hinsichtlich artgerechter Tierhaltung bei

gleichbleibender Wirtschaftlichkeit erforderlich ist.

Appendix

Appendix

Non-elevated perches (NE) Front perch elevated (FE)

Back perch elevated (BE) Stepped position (ST) Figure 1: Schematic cross-section of perch positions within

compartments of small group systems; 1: supply pipe for dust

bathing substrate; 2: back perch; 3: front perch; 4; nipple drinkers.

Figure 2: Cross-section of three-tier small group housing system

Eurovent 625a-EU with non-elevated perches.

4

3 2 1

Big Dutchman, Vechta, Germany

131

Appendix

Figure 3: Compartment of small group housing system Eurovent 625a-EU (60 hens) with

elevated back perches.

Nest box

Front perch Elevated back perch

Dust bath

Dust bath

Back perch

Elevated front perch

Next box

Big Dutchman, Vechta, Germany, modified

Big Dutchman, Vechta, Germany, modified

Figure 4: Compartment of small group housing system Eurovent 625a-EU (40 hens) with

elevated front perches.

132

Appendix

Figure 5: Lohmann Silver laying hens kept in a compartment of

Eurovent 625a-EU with elevated front perches.

Big Dutchman, Vechta, Germany

Figure 6: Compartment of the furnished cage system Aviplus (10 hens).

133

Appendix

Compartment 01 02 03 04 05 06 07 08 09 10 Group size 40 60 60 60 40 40 40 40 60 60 Perch variant NE NE NE NE NE NE NE NE NE NE

Tier 3 LM 3 2 3 LT 3 LT 2 2 LT 3 LM 6 3 LT 2 2 LT 3 LM 9 2 3 3 2 LT LT 2 LT 3 LM 12 3 2 LT LT 2 3

Tier 2 LM 3 3 3 2 LT 2 3 LT

LM 6 2 LT 3 2 LT 2 3 LT LM 9 3 3 3 2 LT 2 LT

LM 12 2 LT 2 LT 2 3 LT 3 Tier 1

LM 3 3 LT 2 2 LT 3 LM 6 2 3 LT 3 LT 2 2 LT 3 LM 9 3 2 2 3 LT LT

LM 12 2 3 LT 3 LT 2 2 LT 3 Figure 7: Number of hens (Lohmann Silver, Lohmann TraditionLT) taken out of

compartments of Eurovent 625a-EU in laying month (LM) 3, 6, 9 and 12 of laying trial

004/2005, Farm Ruthe; NE: perches non-elevated. 2

Compartment 01 02 03 04 05 06 07 08 09 10 Group size 60 40 60 60 40 40 40 40 60 60 Perch variant ST ST BE B BE FE ST ST ST E BE

Tier 3 LM 3 2 2 2 2 LM 6 2 2 2 2 LM 9 2 2 2 2 LM 12 6 6 6 6

Tier 2 LM 3 3 3 3 3 LM 6 3 3 3 3 LM 9 3 3 3 3 LM 12 3 3 3 3

Tier 1 LM 3 3 3 3 3 LM 6 3 3 3 3 LM 9 3 3 3 3 LM 12 3 3 3 3 Figure 8: Number of hens (Lohmann Silver) taken out of compartments of Eurovent 625a-

EU in laying month (LM) 3, 6, 9 and 12 of laying trial 2005/2006, Farm Ruthe; ST: stepped

osition; BE: back perch elevated; FE: front perch elevated. p

134

Appendix

Compartment 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 Group size 60 60 60 60 60 60 40 40 40 40 40 40 40 40 40

T ei r 4 Perch variant NE NE NE NE NE N N NE NE NE N NENE E E NE NE ELM 6 2 2 2 LB 2 LB 2 2 2 LB 2 LB LM 12 2 2 2 LB 2 LB 2 2 2 LB 2 LB

Tier 3 Perch variant N N NE N NE NE N NE NE NE NENE NE E E E NE NE ELM 6 2 LB 2 LB 2 2 2 LB 2 LB 2 2 LM 12 2 LB LB B LB2 2 2 2 L 2 2 2

T ei r 2 Perch variant BE NE BE NE BE NE BE NE BE NE BE NE BE NE BELM 6 LM 12

T ei r 1 Perch variant B B B BE BE BE B BE BE BE BEBE BE E E E BE BE ELM 6 2 2 4 2 2 2 2 LB LB LB LB

LM 12 2 LB 2 LB 4 2 LB 2 LB 2 2 Figure 9: Number of hens (Lohmann Selected Leghorn, Lohmann BrownLB) taken out of

compartments of Eurovent 625a-EU in laying month (LM) 6 and 12 of laying trial

004/2005, Farm Wesselkamp; NE: non-elevated; BE: back perch elevated. 2

Compartment 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 Group size 60 60 60 60 60 60 40 40 40 40 40 40 40 40 40 Perch variant ST ST FE FE BE S ST FE F FE BE B BEB SE T T E E

Tier 4 LM 6 2 2 2 2 2 2 LM 12 2 2 2 2 2 2

T er 3i LM 6 2 2 2 2 2 2 LM 12 2 2 2 2 2 2

Tier 2 LM 6 2 2 2 2 2 2 LM 12 2 2 2 2 2 2

T er 1i LM 6 2 2 2 2 2 2 LM 12 2 2 2 2 2 2 Figure 10: Number of hens (Lohmann Selected Leghorn) taken out of compartments of

Eurovent 625a-EU in laying month (LM) 6 and 12 of laying trial 2005/2006, Farm

esselkamp; ST: stepped position; FE: front perch elevated; BE: back perch elevated. W

135

Appendix

136

t

Compartmen 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 Group size 30 30 30 30 30 30 20 20 20 20 20 20 20 20 20

Tier 4 Perch variant N N NE NE N N NE NE NE E NE NE NE NE E NE NE E ELM 6 2R 1L * 2R* 1L* 2R 1L * 2R* 1L* * * LM 12 2R 1L * 2R* 1L* 2R 1L * 2R* 1L* * *

Tier 3 Perch variant F F F F FE FE FE FE FEFE FE E E FE FE E FE FE ELM 6 2R* 1L* * 2R 1L * 2R* 1L* * 2R 1L LM 12 2R* 1L* * 2R 1L * 2R* 1L* * 2R 1L

Tier 2 Perch variant B F BE FE B F BBE FE E E BE FE BE FE E E BE FE ELM 6 2L 1R * 2R* 1L* 2L 1R * * 2L* 1R* * LM 12 2L 1R * 2R* 1L* 2L 1R * * 2L* 1R* *

Tier 1 Perch variant NE NE NE NE NE N NE N NENE NE NE NE E NE NE ELM 6 * 2R* 1L* 2R 1L 2R* 1L* * 2R 1L LM 12 * 2R* 1L* 2R 1L 2R* 1L* * 2R 1L Figure 11: Number of hens (Lohmann Selected Leghorn, Lohmann Brown*) taken out of

compartments of Eurovent 625A-EU in laying month (LM) 6 and 12 of laying trial

2004/2005, Farm Wesselkamp; NE: non-elevated; FE: front perch elevated; BE: back perch

levated.

t

e

Compartmen 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 Group size 30 30 30 30 30 30 20 20 20 20 20 20 20 20 20

Tier 4 Perch variant NE NE NE NE NE NE NE NE N NENE NE NE NE NE ELM 6 2R 2R 2L 2R 2R 2L LM 12 2R 2R 2L 2R 2R 2L

T ei r 3 Perch variant F F FE FE FE FE FE FE FE FEFE FE E E FE FE FELM 6 2R 2L 2R 2R 2L 2R LM 12 2R 2 2RL 2R 2L 2R

Tier 2 Perch variant B B B BBE BE E BE BE E E ELM 6 2L 2L 2R 2L 2L 2R LM 12 2L 2L 2R 2L 2L 2R

Tier 1 Perch variant NE NE NE NE NE NE NE NE N NENE NE NE NE NE ELM 6 2R 2R 2L 2R 2R 2L LM 12 2R 2R 2L 2R 2R 2L Figure 12: Number of hens (Lohmann Selected Leghorn) taken out of compartments of

Eurovent 625A-EU in laying month (LM) 6 and 12 of laying trial 2005/2006, Farm

Wesselkamp; NE: non-elevated; FE: front perch elevated; BE: back perch elevated.

Appendix

137

Appendix

138

Appendix

139

Appendix Appendix

140

140

Appendix

Figure 17: Normal (grade 4, left), slightly deformed (grade 3, middle) and moderately

deformed (grade 2, right) keel bone.

Figure 18: Severely deformed (grade 1) keel bone after removal of

breast muscles.

141

Appendix

Figure19: Heterophil granulocyte surrounded by erythrocytes.

Figure 20: Lymphocyte surrounded by erythrocytes.

Figure 21: Eosinophil granulocyte surrounded by erythrocytes.

142

Appendix

50%

60%

70%

80%

90%

100%

0 50 100 150 200 250 300 350

Aviplus - LSL EV 625A-EU - LSL

EV 625a-EU - LSL

Figure 22: Laying performance (%) per hen housed of the layer line Lohmann

Selected Leghorn (LSL), trial period 2004/2005, Farm Wesselkamp.

50%

60%

70%

80%

90%

100%

0 50 100 150 200 250 300 350

Aviplus - LB EV 625A-EU - LB

EV 625a-EU - LB


Brown (LB), trial period 2004/2005, Farm Wesselkamp.

143

Appendix

50%

60%

70%

80%

90%

100%

0 50 100 150 200 250 300 350

Aviplus - LSL EV 625A-EU - LSL

EV 625a-EU - LSL


Selected Leghorn (LSL), trial period 2005/2006, Farm Wesselkamp.

50%

60%

70%

80%

90%

100%

0 50 100 150 200 250 300 350

Aviplus - LS EV 625a-EU - LS

Voliere - LS


Silver (LS), trial period 2005/2006, Farm Ruthe.

144

Appendix

100,0 Aviplus - LSL

99,5 EV 625A-EU

99,0 LSL

98,5 EV 625a-EU -LSL

98,0 Aviplus - LSL

97,5 EV 625A-EU -LSL 97,0

96,5 EV 625a-EU -LSL

96,0

95,5

95,0 0 50 100 150 400 200 250 300 350

Figure 26: Survival rate (%) of the layer line Lohmann Selected Leghorn (LSL),

trial period 2004/2005, Farm Wesselkamp.

Figure 27: Survival rate (%) of the layer line Lohmann Brown (LB), trial period

2004/2005, Farm Wesselkamp.

97,0

97,5

98,0

98,5

99,0

99,5

100,0 Av

EA

Ea

Aviplus - LB

EV 625A-EU -LB

EV 625a-EU -LB

0 50 100 150 400 200 250 300 350

145

Appendix

92,0

93,0

94,0

95,0

96,0

97,0

98,0

99,0

100,0

0 50 100 150 200 250 300 350 400

Ea

Avi

Vol

EV 625a-EU - LS

Aviplus - LS

Voliere - LS

Figure 28: Survival rate (%) of the layer line Lohmann Silver (LS), trial period

2005/2006, Farm Ruthe.

146

Appendix

147

Table 1: Number (n), mean ( x ), standard deviation (SD), range (min/max), median ( x~ ) and

25%/75%-quantiles (Q1/Q3) of humerus and tibia bone strength [N], keel bone status, egg

quality traits and egg production per hen present (Farm Ruthe, 2nd trial period, chapter 3).

Trait n x SD min max x~ Q1 Q3 Humerus bone strength (N) 428 205.1 76.2 77.2 511.1 185.4 148.3 256.8 Tibia bone strength (N) 432 135.3 34.2 61.2 284.9 135.9 114.7 153.0 Keel bone status (1-4) 430 3.5 0.7 1 4 - - - Shell breaking strength (N) 3892 42.8 9.3 6.5 71.4 43.6 37.4 49.0 Shell thickness (µm) 3893 344.0 26.5 131 463 344 327 361 Shell density (mg/cm²) 3893 85.7 6.1 51.3 122.2 85.7 81.8 89.5 Shell weight (g) 3893 6.2 0.6 3.3 9.0 6.2 5.8 6.6 Haugh units 3893 82.1 9.2 5.1 107.7 83.2 77.3 88.2 Blood spots (1-2) 3893 0.1 0.3 0 2 - - - Meat spots (1-2) 3893 0.9 0.4 0 2 - - - Albumen height (mm) 3893 7.0 1.3 1.8 11.7 7.0 6.2 7.8 Yolk weight (g) 3891 17.1 1.9 10.0 32.0 17.2 15.9 18.4 Yolk color (1-15) 3893 12.6 0.8 9 15 13 12 13 Egg weight (g) 3893 60.9 4.9 43.5 92.7 60.8 57.5 64.0 Egg production (%) 1152 87.0 0.2 - - - - -

Acknowledgements

Firstly, I sincerely and very gratefully wish to thank Prof. Dr. Dr. habil. Ottmar Distl who

gave me the opportunity to work on this interesting scientific project and who very kindly

provided continous support and help during the preparation of this dissertation.

I am very grateful to my colleague Swaantje Rönchen for providing an excellent working

atmosphere and for bringing up many useful discussions and inspirations, which fruitfully

contributed to the outcome of this thesis.

A special thank goes to Dr. Henning Hamann who guided me throughout the process of

statistical analysis with an excellent knowledge, patience and always in a very friendly

manner.

I would like to thank Deutsche Frühstücksei GmbH, Big Dutchman GmbH and Lohmann

Tierzucht GmbH for their financial support of this project.

I would like to acknowledge Prof. Dr. Ulrich Neumann, PD Dr. Gerhard Glünder and Dr.

Martin Ryll for their scientific and organisational support throughout the trial periods.

I am very glad to mention Sonja Bernhard who was an essential help in conducting laying

hens’ autopsies. Without her very kind support, experiments on these particular trial days

would not have been feasible.

I am very grateful to Harald Ulbrich. He very kindly and encouragingly assisted in bone

dissections and blood sampling.

I would like to thank Mrs Cornelia Mrusek and Mrs Doris Böhm for their kind support in all

kinds of organisational issues. I would also like to mention Jörn Wrede who kindly provided

help in all matters of computing problems.

I am very grateful to Julian Sander and Johanna Siemen for their excellent support in

preparing blood smears and conducting laying hens’ autopsies.

A special thank goes to Dr. Anne Vits and Dr. Daniela Weitzenbürger. They very kindly and

thoroughly introduced my colleague and me to this scientific project, while providing an

excellent working environment.

I would also like to thank Prof. Dr. Marion Hewicker-Trautwein and Dr. Martin Peters for

being an excellent source of advice in helping me evaluate histological keel bone samples.

I am glad to mention Bettina Buck and I would like to thank her for her very friendly and kind

support in preparing histological samples.

I wish to thank Mr Brinkmann for his continous and very reliable support in collecting data at

the trial farm Wesselkamp, Ankum.

I am also grateful to Dr. Christian Sürie for his advice and kind support in all kinds of issues

related to the trial farm Ruthe.

My family deserves a very special acknowledgement for their continous support and care.

Without their help, the preparation of this dissertation thesis would not have been possible.

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