Food evaluation systems Requirements against such systems:

• helps to replace one feedstuff with the other• it should be able to express both the nutrient content of

feedstuffs and the requirements of the animals • the determination of the parameters used for the

calculation should be easy and exact • should not be complicated

Old (natural) evaluation systems : • Thear hay value (1806)

– based on the weight gain of steers with one unit meadow hay

• Scandinavian evaluation system– based on the milk production of cows related to 0.5

kg barley and 0.5 kg oat

Evaluation systems based on the digestible nutrient content:

TDN (total digestible nutrients)

TDN = dig. crude prot. + dig.crude fibre + dig.N-free extr. + 2,25 x dig. crude fat

The calculation of TDN is based on the energy content of the different nutrients:

crude fibre, N-free extract: 17,5 KJ/g crude protein: 24,0 KJ/g

crude fat: 39,5 KJ/g

Gross energy: The heat increment after the total burning of the pure nutrient in oxygen. The so called bomb calorimeters are used for the determination.

TDN was used worldwide in the ruminant nutrition. In the energy evaluation system of ruminants is still used.

nutrient g/kg d.m. digestibility coefficient

factor

crude protein 127,5 0,60 = 76,5

crude fat 50,1 0,60 2,25 = 67,6

crude fibre 319,3 0,65 = 207,5

N-free extract 396,1 0,55 = 217,8

TDN = 569,4 g/kg d.m.

Calculation of TDN (grass silage)

The need for dietary energy:• to produce heat to maintain the body temperature at a higher level than the environment• for the synthesis of large molecules from smaller ones (for the normal replacement of muscle fibres, hormones, enzymes and for tissue growth) and sometimes for their transport in the body• for the contraction of muscle fibres, for breathing, the beating of the heart and for all movement.

The efficiency of the use of food energy for the different purposes is change widely, from about less than 10% (foetal growth) till 60% (growth). The other 90% - 40% appearing as heat.

Units of energyDietary energy is measured in kilocalories (kcal) or in kilojoules or megajoules where:1 kilojoule (kJ) =1000 joules (J)1 megajoule (MJ) = 1000 kJ 1 kcal = 4.184 kJAlthough the joule is the SI unit and so should be the unit of choice, the calorie is also used.

The partition of food energy in the animal pig hen sheep steer

milking cow

GE Gross energy 100 100 100 100 100 faeces 20 30 28 32

DE Digestible energy 80 70 72 68 urine + 3 18* 5 4 4

methan - - 5 6 6ME Metabolisable energy 77 82 60 62 58

heat increment 32 31 32 28 26NE Net energy 45 51 28 34 32

used for maintanance 15 13 18 26 10used for production 30 38 10 8 22

* in poultry species the sum of faces and urine energyTotal heat production of the animal = heat increment + maintenance energy requirement

Choosing among energy systems

Gross energy (GE): Easy to measuer and calculate, however, does not take into account the different digestive characteristics of the animals. So, is not useful for food evaluation.

Digestible energy (DE) (pig, horse, rabbit) : It can be used for these monogastricq animals, because the energy losses related to gases (methan) is low (it is about 0,1-1% of the GE in pigs). Different feedstuffs don’t affect the heat production of the animals.

Metabolisable energy (ME) (poultry): For poultry species it is useful, because the faeces and urin

are excreted together, amount of gas losses is negligible and the feedstuffs for poultry don not have a great impact on the heat production of birds.

Net energy (NE ) (ruminants) : It means the energy content of the food, which left after subtracting all the energy losses. This category is used because the gas losses in ruminants is bigger and the food composition (fibre content) has an influenbce on the heat production of the animals.

- it is difficult to determien, heat increment should be measured

- using in the practice is more complicated

METHODS OF MEASURING ENERGY EXPENDITUREEnergy expenditure can be measured in the following ways:• by direct calorimetry, when all the heat produced by an individual is measured• by indirect calorimetry, measuring oxygen consumption and carbon dioxide production, for which there are various techniques

Energy evaluation system for ruminants in Hungary

change in the composition of the diettran

sfor

mat

ion

coef

fici

ent (

NE

/ ME

)

kg = growth

km = maintanance

kl = lactation

hay barley

– Milking ruminants : • cow, goat : NEl • milking ewe: NEm

– Growing and meat type ruminants:• calf, lamb, beef : NEm + NEg

Determination the energy requirement of animals

0

5

10

15

20

25

30

35

12MJ/kg

12,0MJ/kg

12,5MJ/kg

13MJ/kg

13,5MJ/kg

12,8

grow

th r

ate

Determination the energy content of foods

a., Using animal experiments:

energy consumed (MJ) – energy excreted in the faeces (MJ) DE = ----------------------------------------------------------------------

food intake (kg)

energy consumed (MJ) – (energy excreted in the faeces + urine) (MJ)

ME = -------------------------------------------------------------------- food intake (kg)

b., Prediction:

Equation used for the calculation of energy value of foods:

DE(pig) = 0.0242 x d. cr. prot. + 0.0394 x d. cr. fat + 0.0184 x d. cr. fibre +0.017 x d. N-free extr. (MJ/kg)

DE(horse) = 0.0242 x d.cr. prot. + 0.0341 x d.cr. fat+ 0.0185 x d.cr. fibre+ 0.0170 x d.N-free extr.(MJ/kg)

DE(rabbit) = 0.0221 x d.cr. prot.0.0398 x d.cr. fat+ 0.0176 x (d.cr. fibre+ d.N-free extr.)(MJ/kg)

ME(poultry) = 0,01551 x cr. prot.. + 0,03431 x cr. fat+ 0,01669 x starch + 0,01301 x sugarcompound dietsME(poultry) corn = 0,01515 x cr. prot. + 0,03575 x cr. fat+ 0,01559 x N-free extr. ME(poultry) extr. soybean meal = 0,01569 x cr. prot.+ 0,01941 x cr. fat+ 0,006236 x N-free extr.(MJ/kg)

Ruminants : DE (MJ/kg sz.a.) =TDN x 0.01845ME(MJ/kg sz.a.) =DE x 0.82NEl(MJ/kg sz.a.) =0.6032 x DE x (1-2 df) - 0.502NEm(MJ/kg sz.a.) =1.37 x ME - 0.033 x ME2 + 0.0006 x ME3 - 4.686NEg(MJ/kg sz.a.) =1.42 x ME - 0.041 x ME2 + 0.0007 x ME3 - 6.904

Age Males Females0-3 months 2.28 (545) 2.16 (515)4-6 months 2.89 (690) 2.69 (645)7-9 months 3.44 (825) 3.20 (765)10-12 months 3.85 (920) 3.61 (865)1-3 years 5.15 (1230) 4.86 (1165)4-6 years 7.16 (1715) 6.46 (1545)7-10 years 8.24 (1970) 7.28 (1740)11-14 years 9.27 (2220) 7.92 (1845)15-18 years 11.51 (2755) 8.83 (2110)19-50 years 10.60 (2550) 8.10 (1940)51-59 years 10.60 (2550) 8.00 (1900)60-64 years 9.93 (2380) 7.99 (1900)65-74 years 9.71 (2330) 7.96 (1900)75+ years 8.77 (2100) 7.61 (1810)Pregnancy +0.80* (200)Lactation +1.90 (450)1 month +2.20 (530)2 months +2.40 (570)3 months +2.00 (480)4-6 months +1.00 (240)

Estimated Average Requirements (EARs) for energy for humans, MJday; (kcal/day)

* Last trimester only

•The simplest way to check the adequacy of a healthy individual's diet for energy is to observe their weight over a few weeks. If it is steady so, they are in energy balance, even though their actual weight may not be ideal. •If it is falling, then there is an energy deficit; if rising, then there is an excess of dietary energy, if the individual has stopped growing and is not pregnant.

The amount of food eaten is regulated by the sensations of hunger, appetite and satiety. These sensations are the body's response to signals from a variety of receptors, in the mouth, stomach and in the brain.

Generally over a period of several days the amount of food eaten matches energy output and the body is in energy balance. After a period when too little food has been eaten, appetite will be increased until the weight lost has been replaced. In our society there are several factors which make it very easy for the normal regulating mechanism to be overcome, leading to obesity.

A healthy body contains some fat mainly in fat cells or adipose tissue. Sex and other genetic factors determine its distribution. Typical values for body fat content for men and women in their twenties are 14% and 25% respectively.Obesity is defined as an excessive accumulation of adipose tissue.

Obesity may occur at all ages, although incidence increases with age up to 50 years for men and 65 years for women. It can also be inherited. Very rarely, obesity may be caused by endocrine imbalance or malfunction of the part of the brain controlling appetite and satiety. Experiments have shown individual variation in the amount of deposited fat during overeating and in fat loss after undereating.

Garrow - while investigating the effects of a slimming diet of 800 kcal/day over three weeks, in more than 100 people - found weight loss varied from 1.5 kg to a maximum of 11 kg, following a normal distribution. It must be remembered when helping people to slim.

BODY MASS INDEX (BMI)The BMI, or obesity index is a ratio between weight and height weight in kgheight2 in metres

A high ratio indicates a high weight for height. This may be due to either fat or muscle. Assuming normal muscularity the international consensus isBMI 20-24.9 indicates the desirable range of body weightBMI 25-29.9 is termed overweight BMI 30-40 is obese BMI > 40 is termed very obese

These ratios are not applicable to children.

Silhouettes showing a range of Body Mass Indexes

1. Calculate the DEp, DEh, DEr, MEp, NEl, NEm, NEg content of corn grain!

digestibility coefficientsNutrient content g/kg pig horse rabbit cattle

dry matter 912crude protein 94 0.81 0.61 0.75 0.61crude fat 38 0.65 0.86 0.95 0.86crude fibre 21 0.57 0.49 0.42 0.49N-free extract 745 0.94 0.89 0.91 0.89starch 634sugar 17

df: 0.04

2. Calculate the DE-content of barley if the pigs consumed 10 kg barley, and during the same period excreted 6kg faeces. The GE content of the barley and faeces were 15,8 and 6,9 MJ/kg respectively.

3.Calculate the ME content of extracted soybean meal if the hens consumed 35g soybean meal and the weight of excreta (faeces + urine) was 55g. The GE of soybean and excreta were 17.4 and 5.5 KJ/g respectively.