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EstimatingthecostsofrearingyoungdairycattleintheNetherlandsusingasimulationmodelthataccountsforuncertaintyrelatedtodiseasesARTICLEinPREVENTIVEVETERINARYMEDICINEAPRIL2012ImpactFactor:2.17DOI:10.1016/j.prevetmed.2012.03.004Source:PubMed

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Preventive Veterinary Medicine 106 (2012) 214 224

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Preventive Veterinary Medicine

j our na l ho me p age: ww w.elsev ier .com/ locate /prevetmed

Estima y causing a r undisease

N. Mohd Nora,b,, W. Steeneveldc, M.C.M. Mouritsc, H. Hogeveena,c

a Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, P.O. Box 80151, 3508 TD, The Netherlandsb Department of Preclinical Sciences, Faculty of Veterinary Medicine, University Putra Malaysia, 43400 Serdang, Selangor, Malaysiac Business Economics, Wageningen University, P.O. Box 8130, 6706 KN, Wageningen, The Netherlands

a r t i c l

Article history:Received 31 MReceived in reAccepted 13 M

Keywords:Young dairy caSimulation moCalf diseasesEconomics

1. Introdu

In the Nare culled e

CorresponE-mail add

(N. Mohd Nor)

0167-5877/$ doi:10.1016/j. e i n f o

arch 2011vised form 20 February 2012arch 2012

ttle rearingdel

a b s t r a c t

The costs of rearing young dairy cattle are a part of the cost of the price of milk, as rearingproduces the future dairy cows. As most dairy farmers are not aware of the rearing costs,the rearing of dairy replacements often does not get the attention it deserves. Calculatingthe distribution of the rearing costs throughout the rearing process is difcult as the costsare correlated with biological processes, such as variation in growth rate and disease uncer-tainty. In this study, a calf level simulation model was built to estimate the rearing costsand their distribution from 2 weeks of age until rst calving in the Netherlands. The uncer-tainties related to calf diseases (calf scours and bovine respiratory disease) were included,in which both the probabilities of disease and the effects of diseases (growth reduction)differ at different ages. In addition, growth was modeled stochastically and in a detailedmanner using a two-phase growth function. The total cost of rearing young dairy cattlewas estimated as D 1567 per successfully reared heifer and varied between D 1423 andD 1715. Reducing the age of rst calving by 1 month reduced the total cost between 2.6%and 5.7%. The difference in the average cost of rearing between heifers that calved at 24months and those calving at 30 months was D 400 per heifer reared. Average rearing costswere especially inuenced by labor efciency and cost of feed. The rearing costs of a heiferthat experienced disease at least once (20% of the simulated heifers) were on average D 95higher than those of healthy heifers. Hence, for an individual diseased heifer, disease costscan be rather high, while the relative contribution to the average rearing cost for a standardDutch dairy farm is low (approx. 3%). Overall, the model developed proved to be a usefultool to investigate the total cost of rearing young dairy cattle, providing insights to dairyfarmers with respect to the cost-efciency of their own rearing management.

2012 Elsevier B.V. All rights reserved.

ction

etherlands, on average, 30% of the dairy cowsach year (CRV, 2009) and have to be replaced.

ding author. Tel.: +31 30 252 1887; fax: +31 30 253 1248.resses: N.B.MohdNor@uu.nl, norhariani@putra.upm.edu.my.

Most Dutch dairy farms rear their own young dairy cattleto provide replacement heifers. To produce a good qualityreplacement heifer, well-managed young dairy cattle rear-ing is important. It consists, among other things, of keepinga close check on the weight and age at rst calving (Mouritset al., 2000a; Tozer and Heinrichs, 2001). Nevertheless, asa component of the farm management system, the rearingof dairy replacements often does not get the attention itrequires to be successful (Bach and Ahedo, 2008; Gulliksen

see front matter 2012 Elsevier B.V. All rights reserved.prevetmed.2012.03.004ting the costs of rearing young dair simulation model that accounts fosttle in the Netherlandscertainty related to

N. Mohd Nor et al. / Preventive Veterinary Medicine 106 (2012) 214 224 215

Table 1Probability distributions employed with the specic commands used in @Risk to model the uncertainty and variation in young dairy cattle rearing.

Input variables Command

Month of birth RiskIntUniform (1; 12)Disease

State )Veterinary all prob

GrowthTwo phase

a1 b 308; 340a2 b 236; 270b1 b 150; 175b2 b 520; 570km2 ncate (

ReproductioEstrus det ate: estr

a States hav ease, 4 =b a1 = asymp d phase

second inectc RiskNorm

et al., 2009not aware othe Netherl(CRV, 2009output makeconomic iIf farmers wcost compoit would beon their far

The totaseveral coscosts, barn costs, reproThese cost they are cor1997; Bachoccurrencemortality (Tception (Gamost impodetermines(Mourits etwith milk Heinrichs, 2and Heinric

Various have been 2000; Tozegive good inconsider thin this studfor the uncin growth.

The objemodel to edairy cattleresults of tthe distributhus start toing young farm.

ateria

Model

estimerland

was dn, Redade Codel w

on sysr calves of ag

at thstudy nd rsect ti

2 weeng daservatthy, dirtal, cytudy.

termintions (, barn ed andRiskDiscrete (statesa; states probability call RiskDiscrete (0: 1; 1-call probability: c

growth functionRiskNormal (309; 41.9; RiskTruncate (RiskNormal (237; 48.2; RiskTruncate (RiskNormal (161; 29.5; RiskTruncate (RiskNormal (550; 81.1; RiskTruncate (RiskNormal (0.01128; 0.00157; RiskTru

nection RiskDiscrete (0: 1; 1-estrus detection r

e to be translated to: 1 = healthy, 2 = calf scours, 3 = bovine respiratory distotic BW during the rst phase (kg), a2 = asymptotic BW during the seconion point (d), km = maturation rate.al (mean; standard deviation; RiskTruncate (minimum; maximum)).

b). This is probably because dairy farmers aref the total cost of rearing young dairy cattle. Inands, the average rearing period is 26 months). Such a marked time lag between input andes it difcult for dairy farmers to recognize thempact of rearing decisions made on the farm.ere to become aware of the variation in the

nents related to rearing of dairy replacements, easier for them to apply cost-effective changesms.l cost of rearing young dairy cattle comprisest components, such as healthcare costs, feedcosts, labor costs, costs of breeding, mortalityduction failure costs and carcass removal costs.components are difcult to calculate becauserelated with variation in growth (Mourits et al.,

and Ahedo, 2008) and the uncertainty of the of diseases (Van Der Fels-Klerx et al., 2001),ozer and Heinrichs, 2001), and estrus and con-bler et al., 2000). Growth, in particular, is thertant factor in rearing young dairy cattle as it

the feed costs, rst calving age and weight al., 1999; Gabler et al., 2000) and is correlatedproduction in the rst lactation (Zanton and005; Svensson and Hultgren, 2008; Heinrichshs, 2011).studies on the cost of rearing young dairy cattle

2. M

2.1.

ToNethlevelratio(Palisthe mductiheifeweekplacethis age ato refroma youof ob(healpubethis sis detribucostsculatpublished (Mourits et al., 1999; Gabler et al.,r and Heinrichs, 2001). Although these studiessights into the total cost of rearing, they did note uncertainty related to calf diseases. Therefore,y, a stochastic model is developed to accountertainty related to calf diseases and variations

ctive of this study is to develop a stochasticstimate the distribution of costs during young

rearing in the Netherlands. On the basis of thehis study, farmers can become more aware oftion of costs during young stock rearing, and

prioritize and change the management of rear-stock to improve the protability of the dairy

calving, deain the comreplicationssible rangewere storedInstitute In

Heifer ction of a health. Inpscientic aIf no infor(veterinariaUtrecht Unof the Netused.ability)

)) c

)) c

)) c

)) c

0.01122; 0.01129))c

us detection rate)

dead. (kg), b1 = age at the rst inection point (d), b2 = age at the

ls and methods

development

ate the costs of rearing young dairy cattle in thes, a Monte Carlo simulation model at the calfeveloped in Microsoft Excel (Microsoft Corpo-mond, WA, USA) using @Risk add-in softwareorporation, Ithaca, NY, USA). The settings ofere chosen to represent the Dutch dairy pro-

tem. According to Dutch legislation, new borns are not allowed to leave the farm before 2e. Accordingly, selection of heifer calves takese age of 2 weeks. Thus, the rearing period inis dened as the period between 2 weeks oft calving. In this model, 54 stages were denedme steps in the development for a heifer calfks of age to a fully grown heifer. At each stage,iry animal is characterized by a combinationions including body weight (BW), health statusseased or dead), and reproduction status (pre-clic, pregnant) that we have called states inTransition between these states within stagesed stochastically using various probability dis-Table 1). At each stage, healthcare costs, feedcosts, labor costs and breeding costs were cal-

accumulated from 2 weeks of age until rst

th or age at culling. Considering the variationsbination of states occurring per stage, 20,000

were carried out to obtain insight into the pos- of outcomes. The results of these replications

and were analyzed using SAS version 9.1 (SASc., Cary, NC).alves were simulated assuming the applica-management approach ensuring good herduts were based on information obtained fromrticles, handbooks and webpages (Table 2).mation was available, veterinary expertisens from Faculty of Veterinary Medicine,iversity, and from a practice in the northherlands) and the authors expertise were

216 N. Mohd Nor et al. / Preventive Veterinary Medicine 106 (2012) 214 224

Table 2Input prices for estimating the total cost of young dairy cattle rearing.

Input variable Price (D ) Source

PreventionDehorning at 10 weeks old 11.20/heifer calf Veterinary expertiseAnthelmintic during a grazing season 7.80/heifer Veterinary expertise

Farmers treatmentCalf scours 36/treatment Authors expertiseBovine respiratory disease 5.60/treatment Authors expertise

Veterinary treatmentCalf scours 186/treatment Veterinary expertiseBovine respiratory disease 62.10/treatment Veterinary expertise

Farmers labor 18/h Huijps et al. (2008)Veterinarian labor 100/h Veterinary expertiseBreeding 27/insemination CRV (2009)Feed ration 0.17/1000 VEMa KWIN-V (2007)Milk replacer 1.63/kg KWIN-V (2007)Barn 92/calf/year van Zessen (2005)Heifer calf at 2 weeks old 55/calf LEI (2010)Heifer at 20 months old 475/heifer KWIN-V (2007)Carcass removal

Less than 1 year old 28/carcass Rendac (2010)More than 1 year old 55/carcass Rendac (2010)

a VEM unit is used in Dutch net energy system. 1 VEM unit contains 1.650 kcal net energy.

2.2. Model

2.2.1. StageThe mod

respond tofrom 2 wee(1754) coment intervalof diseases et al., 2009b4 months othe estrus c

2.2.2. StateWithin t

determinesfore the onof rst calvtinuous stacontinuousa minimum

lving. ht of te.ly cal

weig modebovineealth

was demptomxhibitl ill, oms untileifers wonths

nfectio durin). In thd BRDy decie (see

Table 3Transition maH1 = probabiliheifer will bec10% repeated that die within

Stage = x

a The probab Estimates c Estimates

et al. (2009b).d Estimates description

sel consists of 54 stages. The rst 16 stages cor-

intervals of 1 week to reect the time spanks until 4 months of age. The remaining stagesprise intervals of 3 weeks. The need for differ-

s was due to the concentration of the incidencein the rst 4 months of a calfs life (Gulliksen) requiring time intervals of 1 week, and, afterf age, 3 week intervals to match the length ofycle.

she model, BW is the main state variable as it

the development of the heifer calf and there-set of puberty and subsequently the momenting. BW is described in this model as a con-te variable with the use of a stochastic and

growth curve (see next section), ranging from of 43 kg at birth to a maximum of 594 kg

at caweigtissu

Oncauselation(CS), the hstatecal sythat enaveweekthe hto 3 msitic ioccur2001CS anuntarfailurtrix applied with respect to the health status comprising four states (healthy, caty that the young dairy animal remains healthy in the next stage (one minus totaome diseased in the next stage (using incidence risk). H2 and H3 = probability ocases. M1 was set equal to zero assuming only a diseased has the probability of

a specied age period).

Stage = x + 1

Statesa Healthy CS

Healthy H1b S1c

CS H2b S2 BRD H3b 0 Dead 0 0

bility is dependent on previous state at stage = x, calf age and season.based on Bateman et al. (1990), Fodor et al. (2000) and Constable (2004).based on Perez et al. (1990), Menzies et al. (1996), Busato et al. (1997), Svensson

based on Perez et al. (1990), Svensson et al. (2006b), and Gulliksen et al. (2009a).The BW variable represents the actual livehe heifer, corrected for the weight of any fetal

f diseases that occur in the Netherlands andht loss and death were included in the simu-l. Four states were dened (healthy, calf scours

respiratory disease (BRD) and dead) to reectcondition of the simulated heifer. The healthyned as a heifer that does not exhibit any clini-s of disease. The CS state was applied to heifers

clinical symptoms of scours, diarrhea, enteritis,phalophlebitis and umbilical infection from 2

3 months of age. The BRD state was applied toith symptoms of calf pneumonia from 2 weeks

of age, and as BRD after 3 months of age: para-ns were excluded. BRD was considered only tog the winter season (Van Der Fels-Klerx et al.,is model, death only occurred as a result of

(Table 3). Culling, which is the result of a vol-sion, can be the consequence of reproductive

next section).lf scours (CS), bovine respiratory disease (BRD) and dead).l incidence risk). S1 and B1 = probabilities that the healthyf cure from a previous diseased state. S2 and B3 = assumeddeath. M2 and M3 = case fatality risk, proportion of heifers

BRD Dead

B1c M1d

0 M2d

B3 M3d

0 1

et al. (2003, 2006a), Hultgren et al. (2008), and Gulliksen

N. Mohd Nor et al. / Preventive Veterinary Medicine 106 (2012) 214 224 217

To reect the reproduction condition of the simulatedheifer, three states were dened (pre-pubertal, cyclic andpregnant). In order to determine these states, the estrusdetection rate and the conception rate were used (see nextsection).

Heifers cessfully rethe ones thor reproduc

2.2.3. TransTo calcu

model usedDutch studytion (Eq. (1curves that

Yt = a1 + e

where Yt = Bthe rst phakm = maturond phase (t = age (d).

To detercattle rearethe values fstudy (Koena normal dstochastic, ent input vdifferent BW(b1) could oond inectdays (Tablewere similaof each othmaximum vtions gave agrowth ratmeet the Du2008 (CVB,

The growmined direthe previoux + 1). By muhealthy heirate, growtlated heiferand then cusum of BWowing to tha diseased parallel to tThe level oftype of diseKlerx et al.,(Virtala et areduced bythe secondet al., 1996

reduction in growth rate (Van Der Fels-Klerx et al., 2002b).Only a short term effect of reduction in growth rate wasassumed to occur, ranging from 7 days for the diseasesoccurring before 3 months of age to 21 days for diseases

ring aanisme hea

everye risk ty riskapt forge at en in r remainus t

ealthy IR (D

statethere

health. As it abilityted th

a speceriod , CFR a

3 andasonalmint

l impacability

usingtion (7her a he rstfor 2nd; Brick

a succion dionthshs of aonths e, or wulled

EconDutcheks of . By kues eD 55) (ntion

ment of deh

costseifers er for t

and lspent reatme CS cathat reached rst calving were dened as suc-ared heifers. Unsuccessfully reared heifers wereat did not reach rst calving age through deathtive failure.

ition between states within a Stagelate the young dairy cattle BW at each stage, the

the two-phase growth function based on the of Koenen and Groen (1996). This growth func-)) is based on the summation of two sigmoidal

partly overlap.

1km(tb1)

+ a21 + ekm(tb2) (1)

W (kg) at age t (d); a1 = asymptotic BW duringse (kg); b1 = age at the rst inection point (d);ation rate; a2 = asymptotic BW during the sec-kg); b2 = age at the second inection point (d);

mine BW development for healthy young dairyd under Dutch general management conditions,or variables a, b and km were based on the sameen and Groen, 1996) and were modeled usingistribution (Table 1). Since the variables wereeach simulated heifer (replication) had differ-alues for the variables a, b and km to produce a

. For example, age at rst the inection pointccur between 150 days and 175 days and sec-

ion point (b2) could be between 520 and 570 1). For an individual heifer, a, b and km valuesr at each stage. These values were independenter, and were truncated at the minimum andalues around the mean (Table 1). These trunca-

realistic BW and also ensured that the modelede was restricted to a maximum of 1.2 kg/d totch feeding recommendation and standards of2008).th rate (kg/day) of a healthy heifer was deter-

ctly from the growth function, by subtractings BW (stage x) from the current BW (stageltiplying the potential growth rate (kg/day) of a

fer with % disease-induced reduction in growthh loss (kg/day) was obtained. When the simu-

was diseased (state CS or BRD) at stage x + 1red, the BW at stage x + 1 was calculated as the

at stage x plus growth rate that was reducede impact of the disease. As a consequence, forheifer, the growth curve was lower than andhe growth curve of a similar but healthy heifer.

reduction in growth rate was dependent on thease and age (Virtala et al., 1996; Van Der Fels-

2001). CS caused 10% reduction in growth ratel., 1996). For calf pneumonia, growth rate was

23% in the rst month of age to 11% and 2% in and third months of age, respectively (Virtala). After 4 months of age, BRD caused a 30%

occurmechbecam

Atdencfatalito adthe ais givheifeone mthe husingeasedthat Oncestageprobreecwithage pIR, PCTable

Seanthesonaprob

Bydetecwhetfor th19% 2003afterabort15 mmont31 mof agwas c

2.2.4.A

2 wementrevenage (prevetreatcostslaborAll hfarmmenttime per tof thfter 4 months of age. Compensatory weights were not taken into account after the heiferlthy again.

stage, a transition matrix combining the inci-(IR) of diseases, probability of cure (PC), case

(CFR) and repeated cases (RC) was built in order the uncertainty of disease from 2 weeks untilrst calving. An example of a transition matrix

Table 3. H1 represents the probability that theins healthy in the next stage, and is calculated asotal IR. S1 and B1 describe the probabilities that

heifer will become diseased in the next stage,ohoo et al., 2007). The PC from a previous dis-

is represented by H2 and H3. It was assumedis 10% RC which is represented by S2 and B3.y, the heifer could be diseased again in the nextwas assumed that only a diseased heifer has a

of dying, M1 was set equal to zero. M2 and M3e CFR which describes the proportion of heifersic disease that die from it within a specied(Dohoo et al., 2007). The complete overview ofnd RC for all stages and states are presented in

also in Table A1 of Appendix A.lity was modeled to determine the time foric treatment and IR of diseases. To simulate sea-t, month of birth was determined by a uniform

distribution (Table 1). discrete probability distributions for estrus5%) and conception rate, the model determinedeifer had successfully bred. The conception rate

AI was 64% followed by 60%, 61%, 41%, 36% and, 3rd, 4th, 5th and 6th AI, respectively (Bge,ell et al., 2009). First calving age was 9 monthsessful breeding because it was assumed thatd not occur. Since estrus detection started at

(at minimum BW of 360 kg) and ended at 22ge, rst calving age could vary between 24 andof age. If a heifer was not pregnant at 22 monthshen AI was unsuccessful six times, the heifer

because of reproductive failure.

omic components dairy farmer may decide to sell the heifer calf atage or to keep the heifer calf for future replace-eeping the heifer calf, the farmer has reducedqual to the price of a heifer calf at 2 weeks ofTable 2). Total healthcare costs include disease

costs, farmers treatment costs and veterinarycosts. The prevention costs are based on theorning and anthelmintic treatment (including

from the veterinarian and the dairy farmer).infected with CS and BRD were treated by thewo days. The costs included the costs for treat-abor. Labor costs are based on the amount ofon treating the heifer which was for CS 10 minent and for BRD 2 min per treatment. For 25%ses and 10% of the BRD cases, it was assumed

218 N. Mohd Nor et al. / Preventive Veterinary Medicine 106 (2012) 214 224

that the veterinarian was called and performed treatment.These probabilities included the farmers willingness to calla veterinarian (Table 1) considering the labor costs of theveterinarian and the severity of the disease. Subsequently,the farmer continued the treatment for the next two days.The amount of time spent by the veterinarian for treatingCS was 45 min per treatment and for BRD 5 min per treat-ment. In the following 2 days, treatment time was reducedto 10 min per treatment for CS and 1 min per treatmentfor BRD. CS treatment requires more time compared toBRD treatment because, when treating for CS the heifermight need electrolyte treatment and intravenous drip,while for BRD only a parenteral treatment with antibioticsis required.

A heifer calf with a BW less than 42 kg was fed with fourliters of milk replacer per day. A heifer calf with a BW ofmore than 42 kg is fed ve liters milk replacer per day untilits BW reached 73 kg. After 73 kg, the heifer calf was fed twoliters of milk replacer per day, reduced to one liter after78 kg, which continued until weaning (Melkveehouderij,2006). The price for one kg milk powder was D 1.62(Table 2). Weaning is after 10 weeks of age for a heifer calfwith BW of more than 82 kg (Mourits et al., 2000b). Afterweaning, the BW and average weight gain at each stagedetermined the feed energy units (VEM) required, cover-ing the energy requirements for maintenance and growth(CVB, 2008) [VEM is the unit used in Dutch net energy sys-tems for ruminants. One VEM unit contains 1.650 kcal netenergy (Van Es, 1978)]. Besides growth and maintenancerequirements, there was an additional energy requirementduring the grazing season, varying with BW from 250 to950 VEM per day. Further, heifers at the 6th, 7th, 8th and

9th month of pregnancy had an additional energy require-ment of 250,700, 1150 and 1950 VEM per day, respectively(CVB, 2008). The model assumed feed rations to be bal-anced and took into account substitutions of hay, silage,grass and concentrate in the ration. VEM unit price wasbased on the concentrate (940 VEM/kg) price (Table 2). TheVEM unit price was assumed to be reduced by 20% dur-ing the grazing season because there was substitution ofconcentrate and silage with fresh grass, which is cheaper.

Farmers labor costs were based on the time needed tofeed and inspect the calves. This was estimated as 5 min percalf per day before weaning, and 2 min per heifer per dayafter weaning. During the grazing season it was assumedthat labor was 1 min per calf per day. All input prices usedare in Table 2.

The total costs of a successfully reared heifer were cor-rected for the number of heifers that did not successfullyreach rst calving age and were calculated as per Eq. (2):

TCSuccess +(TCDead nDead) + (TCCulled nCulled)

nSuccess(2)

where TCSuccess = average total costs of successfullyreared heifer; TCDead = average total costs of deadheifer; TCCulled = average total costs of culled heifer;nDead = number of dead heifers; nCulled = number of culledheifers; nSuccess = number of successfully reared heifers.

2.2.5. Validation and sensitivity analysisSince no data were available for external validation,

an internal validation was performed. Inputs were com-pared to output to check for consistency and reliability ofthe model output. Sensitivity analyses were performed to

Table 4Inputs change

rce

Disease incidCalf scour terinaryBovine res nsson e

Case fatalityCalf scour ez et al.Bovine res ez et al.

Repeated caBovine res eman eCalf scour terinary

Growth ratea1 and a2 thors ex

ReproductioEstrus det V (2009Articial i thors exConceptio haisri et

PricesConcentra thors exHeifer calf (2010)Heifer thors exLabor thors ex

OthersNon-grazi thors exLabor efc thors ex

Farmers treCalf scour thors ex

Bovine respi thors exVeterinarian

Calf scour terinaryBovine res terinaryd for sensitivity analysis in the model.

Input change Sou

ence risks 8% and +8% Vepiratory disease 0.5% and +0.5% Sve

risks 20% and +20% Perpiratory disease 15% and +15% Persespiratory disease 10% and +10% Bats 10% and +10% Ve

slow and fast10% and +10% Au

nection rate 20% and +20% CRnsemination maximum number 2 and +2 Aun rate 10% and +10% Inc

te D 0.04 and +D 0.04 AuD 29 and +D 27 LEID 100 and +D 100 AuD 18, D 2 and +D 2 Au

ng farm Excluding pasturing Auiency (min/day) 0.5 and +0.5 Auatment time (min/treatment)s 5 and +5 Auratory disease 1 and +10 Au

treatment time (min/treatment)s 15 and +15 Vepiratory disease 5 and 15 Ve expertiset al. (2003), Svensson et al. (2006a), Veterinary expertise

(1990), Svensson et al. (2006a), Gulliksen et al. (2009a) (1990), Svensson et al. (2006a), Gulliksen et al. (2009a)

t al. (1990) expertise

pertise

)pertise

al. (2010)

pertise

pertisepertise

pertisepertise

pertisepertise

expertise expertise

N. Mohd Nor et al. / Preventive Veterinary Medicine 106 (2012) 214 224 219

evaluate the varying effect of input parameters towardseconomic and non-economic output in young dairy cattlerearing. Sensitivity analyses were performed for eco-nomic and non-economic input values (Table 4). Thenon-economic input values analyzed concerned the impactof disease probabilities, growth rate reduction due toimpact of diseases, growth rate, estrus detection rate, con-ception rate, number of AI allowed, labor efciency andtreatment time (Table 4). The variation in growth rate wasdened as a 10% increase of the growth function vari-ables, a1 and a2, resulting in a reduced growth analysis(RG) and an increased growth (IG) analysis, respectively.A sensitivity analysis was also performed for a non-grazingfarm by disregarding the impact of grazing season on feedrequirements and feed price (Table 2).

3. Results

In total, 90.9% of the simulated young dairy cattle suc-cessfully reached rst calving. An additional 6.1% diedprematurely (between 2 weeks until rst calving) and 3%was culled because of reproductive failure. On average,birth weight was 46 kg, and rst calving occurred at 25months of age with an average BW of 542 kg (Table 5).

The total cost of young dairy cattle rearing was D 1567per successfully reared heifer and varied between D 1427and D 1715 (Table 6). Feed costs contributed the most,44.5% (D 69was followheifer calf ccosts (2.5%)reared heifefully reareddifference icalved at 24successfully

The sensues are pres

Table 5Average non-economic output values (595% percentiles given inparentheses).

Output

Birth weight (kg) 46 (44; 49)Weaning weight (kg) 82 (79; 86)Age at rst estrus (months) 15 (15; 16)Weight at rst estrus (kg) 373 (361; 394)Articial insemination 2 (1; 3)Pregnancy age (months) 16 (15; 18)Pregnancy weight (kg) 382 (361; 424)First calving age (mo) 25 (24; 27)First calving weight (kg) 542 (521; 565)Culling age (months) 20a (18; 21)Death age (d) 57b (28; 210)

a Result is from culled heifer due to reproductive failure analysis.b Result is from dead calf analysis.

IR of CS and BRD inuenced the number of dead young dairycattle. Reducing estrus detection by 20% caused an increasein the proportion of culled heifers to 3.6% and also resultedin a higher age at rst calving (25.2 months) and higher rstcalving weight (545 kg). Increasing growth by 10% resultedin heifers that calved earlier (24.4 months old) at a higherrst calving weight (additional 53 kg). Reducing the growthby 10% increased the average rst calving age (27 monthsold) and lowered the average rst calving weight (501 kg).

The resomic iof rear

ed byth ratee labo

eductioreared

cost basturinf D 92erform

Table 6Average econo heifers

Heifer calf pPrevention Farmers treVeterinary tCarcass remFeed 34 (8; 145) 493 (440; 543)Labor 68 (21; 237) 419 (382; 449)Breeding 0.3 (0; 0)b 161 (162; 162)c

Sales 475Barn 9 (2; 44) 140 (129; 150)Subtotal 274 (151; 583) 842 (736; 1006)Average loss Average tota

a The 199%b The rangec The 199%d The avera ge loss of dead young dairy cattle (D 19/successfully reared heifer)

and culled hei Eq. (2).e The averag determined because they were summed up with the average loss

per successful essfully reared heifer varied from D 1427 to D 1715.8), to the total cost of rearing (Table 6). Thised by labor costs (31.8%), barn costs (11.5%),osts (3.5%), healthcare costs (3.1%) and breeding. Culling costs (D 28 on average per successfullyr) and death costs (D 19 on average per success-

heifer) also contributed to the total cost. Then the average rearing cost between heifers that

months and 30 months was almost D 400 per reared heifer.itivity analysis results of the non-economic val-ented in Table 7. Increasing and decreasing the

econcost followgrowing ththe rfully totaling pcost otive p

mic output values, categorized as successfully and unsuccessfully reared

Average costs (D )

Successfully reared heifer (90.9%)

rice 55 27

atment 9 (0; 36) reatment 12 (0; 186) oval

698 (659; 778) 499 (475; 533) 40 (27; 81) 180 (176; 198) 1520 (1427; 1715)

per successfully reared heifer 47d

l rearing cost 1567e

percentiles are D 28 to D 55. is D 0D 27.

percentiles are D 135D 162.ge loss per successfully reared heifer was calculated as the sum of averafer (D 28/successfully reared heifer). For the calculation of losses refer to e total cost of successfully reared heifers 595% percentiles could not bely reared heifer. The 595% percentiles of average subtotal costs per succults of the sensitivity analysis on the non-nput values are presented in Fig. 1. The totaling was especially sensitive to labor efciency,

IR of CS, excluding pasture, conception rates,s, estrus detection rates and IR of BRD. Reduc-r time by min per heifer per day resulted inn of total cost by more than D 100 per success-

heifer. Increase in IR of CS by 8% increased they D 110 per successfully reared heifer. Exclud-g (non-grazing farms) gave an additional total

per successfully reared heifer. Better reproduc-ance, such as increasing the estrus detection

(5% and 95% percentiles given in parentheses).

Dead young dairy cattle (6.1%) Culled heifer (3%)

55 552 (0; 11) 24 (19; 27)32 (6; 72) 10 (0; 36)45 (0; 186) 14 (0; 186)29 (28; 28)a

220 N. Mohd Nor et al. / Preventive Veterinary Medicine 106 (2012) 214 224

Table 7Sensitivity of the non-economic output for different changes in input values.

Inputchange

% Dead youngdairy cattle

% Culledheifer

Average rst calvingage (months)

Average rstcalving weight (kg)

Default situation 6.1 3.0 24.7 542Disease

Calf scours incidence risk 8% 1.9 3.1 24.7 542Calf scours incidence risk +8% 14.8 2.8 24.7 542Bovine respiratory

disease incidence risk0.5% 4.9 3.2 24.7 542

Bovine respiratorydisease incidence risk

+0.5% 8.4 2.9 24.7 542

Calf scours case fatalityrisk

20% 2.4 3.3 24.6 542

Calf scours case fatalityrisk

+20% 11.4 3.1 24.7 542

Bovine respiratorydisease case fatality risk

15% 4.7 3.1 24.7 542

Bovine respiratorydisease case fatality risk

+15% 7.1 3.0 24.6 542

Calf scours repeatedcases

10% 5.5 3.1 24.7 542

Calf scours repeatedcases

+10% 6.3 2.9 24.6 542

Bovine respiratorydisease repeated cases

10% 5.9 3.0 24.7 543

Bovine respiratorydisease repeated cases

+10% 6.2 3.1 24.7 542

GrowingIncreased growth +10% 5.9 3.0 24.4 595Reduced g

ReproductioEstrus detEstrus detConceptioConceptio

rate (20%), increasing cfully rearedand increascosts of D 41tively. Increcost by D 19

Fig. 1. Sensitivper day; LE-0.58%; NGF = nonreduced by 10increased by 0rowth 10% 6.1 3.2 nection 20% 6.1 3.2 ection +20% 6.3 3.1 n rate 10% 6.2 7.1 n rate +10% 5.9 1.1 saved D 17 per successfully reared heifer whileonception rate by 10% saved D 30 per success-

heifer. The results also showed that reducinging the growth by 10% resulted in additional

and D 43 per successfully reared heifer, respec-ase in the IR of BRD by 0.5% increased the total

per successfully reared heifer.

The sensheifer to thThe reductcost by D 61opportunityare D 0) redreared heife

-150 -100 -50 0

BRDIR+0.5%

ED+20%

ED-20%

RG

IG

CR+10%

CR-10%

NGF

CSIR -8%

CSIR+8%

LE-0.5min

LE+0.5min

Change in the total cost () of rear

ity of the total cost of rearing per successfully reared heifer for different non-econ min = labor efciency reduced 1/2 min per day; CSIR + 8% = calf scours incidence ris-grazing farm; CR-10% = conception rate reduced 10%; CR + 10% = conception rate%; ED + 20% = estrus detection increased 20%; ED-20% = estrus detection reduced 2.5%.26.7 501

25.2 54624.3 54024.8 54324.5 541itivity of the total cost per successfully rearede economic input values is presented in Fig. 2.ion in the labor cost by D 2 reduced the total

per successfully reared heifer. Considering no costs for the farmers own labor (i.e. labor costsuced the total cost by D 520 per successfullyr.

15010050

ing

omic input. LE + 0.5 min = labor efciency increased 1/2 mink increased 8%; CSIR-8% = calf scours incidence risk reduced

increased 10%; IG = growth increased by 10%; RG = growth0%; BRDIR + 0.5% = bovine respiratory disease incidence risk

N. Mohd Nor et al. / Preventive Veterinary Medicine 106 (2012) 214 224 221

50

LC+2

Conc-0.04

Conc+0.04

t () of

Fig. 2. Sensiti ent inpuConc-0.04 = co labor coCP-20 = heifer eifer pr

4. Discussi

The averestimated aPreviously,and D 1134not taking labor costs were excludper successrearing in testimated acustom opestressing thcomparison

Based oaverage at average agobserved inis 26 monthing age ranis larger anthermore, orearing conaccount. Foat 15 monthcontrast, da15 monthsnecessary, months to 3

The growsuccessfullying, feed coour use of several advactual dataalso been inaccurate esgrowth curvuate the cos

growinimal) on herefoect ping di

ently, acosts age of r rearinr.ere ar

the a until rs wash was s decid

and ductio

rst ceductKlerx ermed 0-50-100-150-200

HP-100

HP+100

CP-20

CP+27

LC-2

Change in the total cos

vity of the total cost of rearing per successfully reared heifer for differncentrate price reduced D 0.04; LC + 2 = labor costs increased D 2; LC-2 =

calf price reduced D 20; HP-100 = heifer price reduced D 100; HP + 100 = h

on

age total cost of rearing young dairy cattle wass D 1567 per successfully reared heifer (Table 6).

the total costs were estimated between D 907 for Dutch circumstances (Mourits et al., 2000b),ination rate into account. Within these costs,were excluded. In our study, when labor costsed, the average total cost of rearing was D 1047fully reared heifer. The estimated total cost ofhe US (Gabler et al., 2000) was lower, and wass D 714 and D 788 (including labor costs) forrations and milking operations, respectively,e difference in production circumstances in

to the Dutch situation.n the simulation results, calving occurred onthe age of 25 months (Table 5). The simulatede of 25 months is lower than what has been

practise (average Dutch heifer rst calving ages (CRV, 2009)). This is due to the limited calv-

ge (2427 months), while in practise this ranged more skewed (Mourits et al., 2000b). Fur-ur model simulated heifer calves under good

whenthe mmodeand tto rebreedsequfeed the aloweearlie

Thsuredbirthheifewhicit wabelowas reuntilrate rFels-conditions, and extreme values were not taken intor instance, breeding was started not earlier thans of age and AI was allowed up to six times. Iniry farmers in practise breed their heifers before

of age and breed more than six times whenresulting in rst calving ages varying from 226 months (Mourits et al., 2000b).th curve used in the model we developed has

determined the age for weaning and breed-sts, rst calving age and weight. In addition,

a stochastic and continuous growth curve hasantages. Firstly, the growth curve is based on

in the Netherlands. Secondly, variations havecluded in the data. Consequently, these gave antimation of the total cost of rearing. Because thee settings were exible, it was possible to eval-ts at different growth rates (Fig. 1). In this study,

situation.The effe

calving weiincluded inpicture thecially as farMany studing age animpact on mHeinrichs, 2and Heinricnutritional growth ratchallenges (Drackley, 2values for Bwithin esta200150100

rearing

t prices. Conc + 0.04 = concentrate price increased D 0.04;sts reduced D 2; CP + 27 = heifer calf price increased D 27;

ice increased D 100.

th was increased by 10%, the heifer reachedl breeding weight (which was 360 kg in our

average at 13 months of age (data not shown),re could have been bred at that age. However,ractise, it was assumed within the model thatd not occur before the age of 15 months. Con-

10% increase in growth resulted in additionals breeding was unnecessarily postponed until15 months. So, with 10% increase in growth,g costs could be expected if the heifers are bred

e no studies known by the authors that mea-ctual growth curve of diseased heifers fromrst calving. In most studies, BW in diseased

measured at a certain age or at rst calving,not detailed enough for this model. Therefore,ed that the diseased growth curve should run

parallel to the potential healthy growth curve,n in growth after being diseased can persistalving (Smith, 1998) [The inputs on growth

ion were from Virtala et al. (1996) and Van Dert al. (2002a)]. In addition, a eld veterinarian

that these inputs are applicable for the Dutchct of growth rate, rst calving age, and rstght on rst lactation milk production was not

this model. However, for a complete economicse effects need to be taken into account, espe-mers are aiming at optimizing milk production.ies have shown that growth rate, rst calv-d rst calving weight can have a signicantilk production in the rst lactation (Zanton and005; Svensson and Hultgren, 2008; Heinrichshs, 2011). Furthermore, calves with improvedstatus in the rst 23 weeks of age have a highere and are better able to withstand infectiousand produce more milk in the rst lactation005). The simulated calves in our model showW, growth rates and rst calving age that fallblished values (Zanton and Heinrichs, 2005; Le

222 N. Mohd Nor et al. / Preventive Veterinary Medicine 106 (2012) 214 224

Cozler et al., 2008), which would imply that no negativeimpacts can be expected for milk production capacity.

Labor costs were estimated to be D 18 per hour (Huijpset al., 2008). Dutch farms are mainly family businesses, andtherefore thlabor differon their owas zero. Thlower than heifer.

The mor6%, with moThe mortaliHeinrichs, 1Norway (7.of excludinDutch circuand at the and 2.3% (Pdid not inclbecause of odystocia).

There wthan D 100 pincreased (Fand reducincost of rearof diseases the results oin disease icalving weithe inputs herd healthinstance, difeeding colotity and prostock to groSecondly, itstage, altho(Van Der Fethe disease7 days befoin growth are extremegrowth thacompensatreality thismade of a dairy cattle2002a). In aboth CS anders (Heinricthe effect oon age at reffects of grToews et alet al., 2002a

The totaease at leastD 95 higher(data not sh

disease costs can be rather high while their contributionto the average total cost is minor (Table 6). However, thiscontribution will, to some extent, be underestimated as aconsequence of the assumptions made. Therefore, it will be

sary tses bee mod

of futumbiniully rethe ge

farm ( of milper hecost oprice oers to ring y

nclus

stochaand di

cattleully re5. Theat leasthighedividu

whileost forThe too the enougconomodel de tota

t fromhanginrotab

owled

e auter Minysia (U

many aul Dobinary M

ndix A

e Tabl

ences

A., Ahedt. Clin. NR., 2003ifers: remest. Ae level of opportunity costs due to additionals among farms. Most Dutch farmers who workn farm perceived the opportunity costs of laborus they will estimate the total cost of rearingour estimation of D 1567 per successfully reared

tality risk from 2 weeks until rst calving wasrtality occurring on average at 57 days of age.ty is lower than in the US (9.4%) (Losinger and997), Denmark (8.6%) (Nielsen et al., 2010), and8%) (Gulliksen et al., 2009a). But this is a resultg the mortality in the rst 2 weeks of life. Formstances, the calf mortality within 24 h of birthrst week of age are 6.9% (Harbers et al., 2000)erez et al., 1990), respectively. Also, the modelude disease outbreaks, and death did not occurther diseases or conditions (e.g., accidents and

as an increase in the total rearing costs by moreer successfully reared heifer when IR of CS wasig. 2). This showed that calf health is importantg the incidence of disease can lower the totaling. However, although an increase in the IRincreased the total cost of young stock rearing,f the sensitivity analysis showed that a changenputs did not affect rst calving age and rstght (Table 7). These results can be explained byused and the assumptions made. Firstly, good

management was assumed, which includes, forsinfecting the navel appropriately after birth,strum at an appropriate time in enough quan-viding a conducive environment for the youngw (Bach and Ahedo, 2008; Beam et al., 2009).

is assumed that only one disease occurs in oneugh in reality these diseases can occur togetherls-Klerx et al., 2002a). Thirdly, the duration ofs is conned to a single stage, which is onlyre 3 months of age. Fourthly, the reductionsrate for CS and BRD before 3 months of agely low (Virtala et al., 1996) and the maximum

t occurs between 3 months and 7 months coulde for the loss before the age of 3 months. In

is not conclusive because no study has beencompensatory weight mechanism after young

have been diseased (Van Der Fels-Klerx et al.,ddition, treatment before 4 months of age for

BRD showed a positive effect on height of with-hs et al., 2005). According to previous studies,f the diseases on later stages of rearing periodst calving were ambiguous and the short termowth on later breeding were not clear (Waltner-., 1986; Virtala et al., 1996; Van Der Fels-Klerx).l cost of rearing a heifer that experienced dis-

once (20% of simulated heifers) was on average than that of heifers that are not infected at allown). Hence, for an individual diseased heifer,

necesdiseacan btopic

Cocessfwith dairypricemilk total cost farmof rea

5. Co

A cost dairycessfD 171ease D 95 an inhigh,ing c3%). 13% thigh the ethe ming thbeneand cthe p

Ackn

ThHighMalaAlso,Ing PVeter

Appe

Se

Refer

Bach, Ve

Bge, heDoo explore the consequences of transmission oftween young dairy cattle. Such consequenceseled in a herd-level model, which will be there work.ng the results on total cost (D 1567 per suc-ared heifer) and rst calving age (25 months)neral characteristics of a standardized Dutch100-cow herd, 29% dairy cow replacement, costk of D 0.466/kg and a production of 795,300 kgrd per year (LEI, 2010)), demonstrates that thef rearing contributes approximately 13% to thef milk. This value indicates the necessities forbe more aware of the economic consequencesoung dairy cattle in their dairy enterprise.

ion

stic model was developed to estimate the totalstribution of costs during the rearing of young. The total cost of rearing was D 1567 per suc-ared heifer and varied between D 1423 and

cost of rearing a heifer that experienced dis- once (20% of simulated heifers) was on averager than that of uninfected heifers. Hence, foral diseased heifer, disease costs can be rather

the relative contribution to the average rear- a standard Dutch dairy farm is low (approx.tal cost of rearing contributed approximatelycost price of milk. In our opinion, this value ish for dairy farmers to become more aware ofic importance of replacement rearing. Overall,eveloped is a detailed, useful tool in calculat-

l cost of rearing young dairy cattle. Farmers can the awareness it provides to start prioritizingg rearing management accordingly to improveility of their farm.

gments

hors would like to acknowledge Malaysianistry of Education (MOHE) and Universiti PutraPM), Malaysia for the funding of this project.thanks to Dr Mirjam Nielen, Dr IJmert de Vries,belaar and Dr Harm Ploeger, from the Faculty ofedicine, Utrecht University for their expertise.

.

e A1.

o, J., 2008. Record keeping and economics of dairy heifers.. Am. Food Anim. Pract. 24, 117138.

. Conception rates after AI in Swedish red and white dairylationship with progesterone concentrations at AI. Reprod.nim. 38, 199203.

N. Mohd Nor et al. / Preventive Veterinary Medicine 106 (2012) 214 224 223

Table A1Transition matrix combining probabilities and risks. Probability of remaining healthy (H1) in healthy young dairy cattle, incidence risk for calf scours (S1)in healthy young dairy cattle, incidence risk for bovine respiratory disease (B1) in healthy young dairy cattle, case fatality risk for calf scours (M2), casefatality risk for bovine respiratory disease (M3), the probability of cure when infected with calf scours (H2) and the probability of cure when infected withbovine respiratory disease (H3) adapted in the presented model for the winter season (indoor feeding regime).

Age (d) H2

21 0.61 28 0.60 35 0.60 42 0.60 49 0.80 56 0.80 63 0.80 70 0.80 77 0.80 84 0.80 91 0.80 98 1

105 1 112 1 119 1 126 1 147168 189210 231 252273 294 315 336357 378 399420 441462 483 504 525 546567 588609 630 651672 693 714 735 756

a The incide

Bateman, K.G.tion of antdisease. Ca

Beam, A.L., LHicks, J.Atransfer omanagem3973398

Brickell, J.S., Bgrowth anfertility of408416.

Busato, A., Stehealth in c

Constable, P.DJ. Vet. Inte

CRV, 2009. InDutch). CRjaarverslaH1 S1 B1a

0.9103 0.086 0.0037 0.9102 0.082 0.0078 0.9107 0.080 0.0093 0.9886 0.004 0.0074 0.9929 0.003 0.0041 0.9934 0.003 0.0036 0.9956 0.001 0.0034 0.9942 0.002 0.0038 0.9935 0.002 0.0045 0.9957 0.002 0.0023 0.9956 0.001 0.0034 0.9945 0 0.0055 0.9963 0 0.0037 0.9942 0 0.0058 0.9949 0 0.0051 0.9967 0 0.0033

0.9965 0 0.0035 1 0.9966 0 0.0034 1 0.9910 0 0.0090 1 0.9938 0 0.0062 1 0.9930 0 0.0070 1 0.9952 0 0.0048 10.9961 0 0.0039 1 0.9961 0 0.0039 1 0.9961 0 0.0039 1 0.9961 0 0.0039 1 0.9961 0 0.0039 1 0.9961 0 0.0039 1 0.9961 0 0.0039 1 0.9985 0 0.0015 1 0.9997 0 0.0003 1 0.9997 0 0.0003 1 0.9997 0 0.0003 1 0.9997 0 0.0003 1 0.9997 0 0.0003 1 0.9997 0 0.0003 1 0.9997 0 0.0003 1 0.9997 0 0.0003 1 0.9997 0 0.0003 1 0.9997 0 0.0003 1 0.9997 0 0.0003 1 0.9997 0 0.0003 1 0.9997 0 0.0003 1 0.9997 0 0.0003 1 0.9997 0 0.0003 1 0.9998 0 0.0002 1

nce after 91 days during other seasons is zero.

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0.29 0.78 0.120.30 0.78 0.120.30 0.71 0.190.30 0.71 0.190.10 0.71 0.190.10 0.71 0.190.10 0.71 0.190.10 0.71 0.190.10 0.71 0.190.10 0.71 0.190.10 0.71 0.190 0.71 0.190 0.73 0.170 0.73 0.170 0.73 0.170 0.73 0.17

0 0.71 0.190 0.72 0.180 0.74 0.160 0.74 0.160 0.74 0.160 0.74 0.160 0.74 0.160 0.74 0.160 0.74 0.160 0.74 0.160 0.74 0.160 0.67 0.230 0.67 0.230 0.67 0.230 0.67 0.230 0.67 0.230 0.64 0.260 0.64 0.260 0.64 0.260 0.64 0.260 0.64 0.260 0.64 0.260 0.64 0.260 0.64 0.260 0.64 0.260 0.64 0.260 0.64 0.260 0.64 0.260 0.64 0.260 0.64 0.26

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