Physico-chemical Evaluation of Feeds

7/25/2019 Physico-chemical Evaluation of Feeds

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PHYSICO CHEMICAL

ANALYSIS

FEED EVALUATION

by

Margarita T. Arnaiz


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OUTLINE

1. Introduction2. Physical evaluation

3. Chemical evaluation

a. proximate analysismoisture, crude protein, crude fat, crude fiber, ash, NFE

b. specific nutrient content

amino acids, fatty acids, vitamins and minerals

c. anti-nutrient contents

d. others

4. Exercise (problem solving)


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Feed and ingredient evaluation

important to ensure effectiveness of feeds

to provide optimum growth of the animals

no single test will provide necessary data

for adequate feed evaluation variety of tests methods are utilized to

provide information required to assess the

quality and nutritional value of feeds


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Evaluation methods

Physicalrely on the physical characteristics of

feedstuffs but little information on the nutritional value

Chemicalcharacterize or define the chemical nutrients

present

Biologicalutilized live organisms, i.e., actual feeding

experiment; ascertains the true value of the feedstuff to

the animal; time-consuming, expensive, and requires

facilities for holding the animals

Microbiologicaluse of microorganisms to evaluate

presence of nutrients;


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Physical Evaluation

Use of sensesmellrancidity of oil

tasteoff flavors

visualextraneous matters; homogeneity of ingredients

touchwetness, dryness

Attractabilityhow fast the animal is attracted

Bulk densitywt in gram/liter

Water stability test-weight loss after it is placedin water after a certain period


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Chemical Evaluation

Proximate analysis Developed by Wendee Experimental Station in

Germany over a 100 years ago

most generally used chemical scheme for describingfeedstuffs

general overview of the chemical composition feeds,

partitioning compounds with common chemical

properties


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Proximate analysis

Moisture

Crude protein

Crude fat or ether extract Crude fiber

Ash

Nitrogen free extract


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Flow Diagram for Proximate analysis

Feed sample

Oven dry@ 105C

Moisture

Moisture free sample

Incinerate@600C

Ash

Crude protein, CP

100-(CP+Cft+Cfb+Ash) NFE Crude fiber, Cfb

Boil in acid, boil in alkali

Oven dry@105C, incinerate

@ 550C

Fat free residue

DigestionDistillation

TitrationCrude fat, Cft

Ether extraction


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Sample preparation

grinder

formulated feed

as receivedGround feed

% moisture determination

Other proximate components

Oven dry @ 105 to

remove moisture


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Moisture

Loss in weight after oven drying at

105 - 135oC

High moisture content can lead to

growth of molds during storage

Moisture content should not be

more than 10% prior to storage

Reference Test method

-AOAC 930.15 (oven method)

-Moisture analyzer

Moisture

analyzer

Oven


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Crude protein (CP) Proteins are complex nitrogenous cmpds essential to life; source

of energy Kjeldahl technique of analysis

-developed byJohan Kjeldahl (1883)

- discovered that proteins contain more or less 16% nitrogen

ReferenceTest method :AOAC 984.13

Principle: Sample is digested in H2SO4, using CuSO4catalyst,

converting N to NH3, which is distilled and titrated

Steps

1.Digestionnitrogenous cmpds added with H2SO4 to break N bonds, forming NH4+

2: Distillation - NH4+is converted to NH3 (g) by NaOH, NH3(g) is distilled into acid soln3.Titration - Unreacted acid titrated with NaOH

Calculation: Nitrogen = (ccxN)acid-(ccxN)base x 14.0067

%Nitrogen =(Wt N/wt sample) x 100

%CP = 6.25 X Nitrogen


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Crude protein analysis by Kjeltec method

(automatic distillation and titration)

Digestion at 420oC

Catalyst,

CuSO4+K2SO4

H2SO4,conc

6 mL

Spl, 0.1g Digested sample

1.Insert tube with digestedspl

2.Input weight

3. Automatic distillation

and titration

4. Read out % CP

(Factor 6.25)

To Kjeltec apparatus

3.1.NaOH added,

3.2.NH3(g) directed towards vessel

with boric acid + indicators

3.3.Titration with std acid (HCl) with

end point electrode sensor

3.4. automatic calculation of %Cp


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Conversion factors for some protein sources

Origin Per cent N in protein,

%

Conversion Factor

Oil seed

proteins

18.5 5.4

Cereal

proteins

17 5.9

Plant leaf 15 6.6Animal or fish 16 6.25


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Crude fat/ether extract Material extractable with organic

solvent, e.g. ether Extractable matters incl lipids, fat

soluble vitamins (A,D&E), some cmpds

with little nutritional value to animals

(chlorophyll, volatile oils, resins

pigments, waxes) Soxhlet method of analysis

ReferenceTest method: AOAC 991.36

(Using SOXTEC 2055)

Soxhlet apparatus (conventional)

Soxtec 2055 (automated)

Steps;

1. boiling in solvent (petroleum ether)2. Draining of solvent

3. Recovery of solvent

4. Drying of cups with fat residue at 105oC

Calculation :

%Fat = [(Wt cup with fat residue-Wt cup) /Wt sample]x100


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Crude fiber Refers to the residue of a feed that is

insoluble after successive boiling in acid and

base Generally regarded as the indigestible

portion of carbohydrate having no nutritional

value

Method of determination simulates the

digestive tract, acidic in the stomach and

alkaline in the small intestine

Reference Test Method : AOAC 978.10

using Fibertec 1020

Steps:

1. Defatted sample in fritted glass crucible

boiled with acid, filtered & wash with water

2. Boiling with alkali, filtered & wash with water

3. Drying at 105oC

4. Ashing at 500oCFibertec

Calculation: % Cfb = [(Wt at 105oCWt at 500oC)/ initial Wt sample] x100


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Ash

Inorganic residue

obtained by burning off

organic matter

Residue after burning

allows for mineral analysis

Reference Test Method:

AOAC 942.05

Sample is burned in

furnace for 2 hours at

600oC. The loss in weight

is the amount of ash.

Furnace


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Nitrogen-free extract (NFE)

Represents supposedly the soluble

carbohydrate of the feeds, but may also

contain hemicellulose and lignin

Determined by mathematical calculation

% NFE = 100 (%Cft + % CP + % Cfb+%Ash)


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Summary of proximate analysis

Component Reference Test Method Determination

Moisture a)AOAC 930.15: Moisture in Animal Feed

b) Moisture analyzer (Mettler Toledo MJ33)

Loss in weight after drying x 100

a)Loss in weight after drying x 100b) direct reading

Crude fat/ether

extract

AOAC 991.36: Fat (Crude) in Meat and Meat

Products

(by SOXTEC 2055)

(Wt fat residue*/wt of sample)x 100

*with blank correction

Crude fiber AOAC 978.10: Fiber (Crude) in animal Feedand Pet Food

(By FIBERTEC M6 1020)

[(Wt at 105-wt at 500)*/initial weight] x100

*with blank correction

Crude protein (by KJELTEC 2300)) AOAC 984.13: Protein

(Crude) in Animal and Pet Food

% N x 6.25)

Ash AOAC 942.05: Ash of Animal Feed Loss in weight after ashing x 100

NFE By difference 100-(CP+Cfb+Cft+Ash)


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Energy content

Can be measured directly

using the bomb calorimeter

Indirectly from theestimated composition (i.e.

protein, lipid, &

carbohydrates) by

multiplying the energy

conversion factor for eachnutrient and summing them

Bomb calorimeter

www.techknow.org.

uk


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Specific Nutrient contents

Amino acids

Fatty acids

Vitamins

Minerals

Endogenous (urease,trypsin inhibitors, etc)

Exogenous ( aflatoxins, pesticides, heavy metals, etc)

Feed additives

Antibiotics, antioxidants ( ex. Ethoxyquin)

Anti-nutrient contents


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Amino acids

Amino acids (AA) can be

analyzed using a dedicatedamino acid analyzer or high

performance liquid

chromatograph (HPLC)

Purified proteins are hydrolyzed

and injected in HPLC withfluorescence detector and cat-

ion exchange resin column.

Mobile phase with varying ionic

strength and pH carries the

sample across the columnwhere separation of different AA

takes place. Identification and

quantification is effected by

calibration of an AA standard

solution

HPLC


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Fatty acid Fatty acids serve as source of

energy for many physiological

functions in organisms Can be analyzed using gas

chromatograph (GC) with flame

ionization detector

Lipid/fat are extracted from the

sample using organic solvents(chloroform-methanol),

saponified and formed into

esters prior to injection in the

GC. The sample upon injection

is carried by an inert gas (e.g.He) across a capillary column

where separation takes place.

Identification and profiling is

aided by a mixed fatty acid

standard.

GC


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Vitamins

Variety of nutrients whichdo not include proteins,

lipids, and carbohydrates

Required in small

amounts for normal

growth

Can be water soluble

( thiamin, riboflavin,

ascorbic acid, etc)

Some vitamins can be

analyzed using HPLC

Inorganic components

which can be analyzed

from the ash (Ca, P, Fe,

etc)

Can be analyzed using

atomic absorptionspectrophotometer

(AAS), inductively

coupled plasma (ICP),

and also by colorimetricmethods

Minerals


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Anti-nutrients determination

Substances that can affect the health and

normal performance of the animal, either

toxic or inhibit metabolic reactions

Trypsin inhibitors - spectrophotometry

Aflatoxin - chromatography

PesticidesGas Chromatography

Heavy metals - AAS


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Feed additives

Feed components that can affect food safety of

aquaculture products

Antibiotics

- added to feeds to control diseases (treatment and

prophylaxis) or as growth enhancer

Anti-oxidants

- added to feeds to prevent their deterioration, especially

oxidation of fats (prevention of rancidity), ex. Ethoxyquin

Mostly analyzed and widely accepted method of analysis

is by the use of HPLC


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Shake & centrifuge

Solvent removal

Filter

( 0.22m membrane filter)

Inject in HPLC

Homogenize

Sample preparation, extraction and HPLC analysis for antibiotics

Analysis & quantification

Sample


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Exercises for proximate analysis

Moisture Wt of dish Wt initial Wt Final %Moisture Average

Trial 1 22.0879 24.3992 24.3435

Trial 2 24.8102 26.9212 26.7729

Ash Wt crucible Wt Spl Wt crucible+ash %Ash

Trial 1 19.3038 2.0211 19.9151

Trial 2 20.6886 2.0121 21.2946

CP Wt sample % N %CP

Trial 1 0.1019 8.857

Trial 2 0.1063 8.8684

CFt Wt cup Wt sample Wt cup +fat %Cft

Trial 1 22.397 1.0009 22.4229*

Trial 2 22.3373 1.0422 25.3678*

Cfb Wt crucible @

105

Wt crucible @500 Net wt of Cfb % Cfb

Trial 1 29.517 29.49 0.0188*

Trial 2 27.0086 27.0086 0.0139*

With blank correction

Problem: Estimate the nitrogen free extract (NFE) of the sample


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THANK YOU


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Exercises for proximate analysis

Moisture Wt of dish Wt initial Wt Final %Moisture Average(%)

Trial 1 22.0879 24.3992 24.3435 11.31 11.32

Trial 2 24.8102 26.9212 26.7729 11.33

Ash Wt crucible Wt Spl Wt crucible+ash %Ash

Trial 1 19.3038 2.0211 19.9151 30.25 30.18

Trial 2 20.6886 2.0121 21.2946 30.12

CP Wt sample % N %CP

Trial 1 0.1019 8.857 55.36 55.39

Trial 2 0.1063 8.8684 55.43

CFt Wt cup Wt sample Wt cup +fat %Cft

Trial 1 22.397 1.0009 22.4229* 2.59 2.76

Trial 2 22.3373 1.0422 25.3678* 2.93

Cfb Wt crucible @

105

Wt crucible @500 Net wt of Cfb % Cfb

Trial 1 29.517 29.49 0.0188* 1.88 1.61

Trial 2 27.0086 27.0086 0.0139* 1.33

With blank correction

Problem: Estimate the nitrogen free extract (NFE) of the sample (10 O6%)

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Physico-chemical Evaluation of Feeds

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