1. Methods adopted for assessing
energy and protein
requirements in Livestock
Dr. Pankaj Kumar Singh
Assistant Professor,
Deptt. of Animal Nutrition,
Bihar Animal Sciences University, Patna
E-mail: vetpank@gmail.com
2. Why to Determine Energy and
Protein requirement of
Livestock and Poultry?
3. ENERGY REQUIRMENTS FOR MAINTENANCE
Maintenance requirement
• The maintenance requirement of a nutrient can be
defined as the quantity which must be supplied in the
diet so that the animal experiences neither net gain
nor net loss of the nutrient.
• An animal is in a state of maintenance when the
amount of nutrients in the feed will maintain the
animal in equilibrium i.e., body composition remains
constant and is not growing, not working or not
giving any product as milk or mutton or egg.
• This minimum demand of feed is the maintenance
requirement.
4. ENERGY REQUIRMENTS FOR MAINTENANCE
• If this need is not met, the animals are forced to
draw upon their body reserves to meet their
nutrient requirements for maintenance, commonly
revealed by a loss in weight and other undesirable
consequences.
• The destruction of body tissue is referred to as
fasting catabolism.
5. ENERGY REQUIRMENTS FOR MAINTENANCE
• Fasting catabolism
• In the absence of feed, the nutrients required to support
the activities essential to life (viz, respiration, circulation,
maintenance of muscular tonus, manufacture of internal secretions,
etc. ) come from the breakdown of body tissue itself.
• This destruction of body tissue is referred to as the
fasting catabolism and it can be measured in terms of
the waste products eliminated through the various paths
of excretion.
• Most of the tissue breakdown occurs to meet the demand
of the fasting organism for energy for its vital processes.
6. BASALAND FASTING METABOLISM
Basal Metabolism refer to the heat production of an
animal resting in a thermally neutral environment
(25oC) and in a post-absorptive state (that is after
the digestion and absorption of the last food
ingested has stopped).
7. Conditions essential for measuring BMR :
1) Good nutritive condition: Previous diet of the animal has been adequate.
Poor state of previous nutrition tends to decrease basal heat production.
2) Environmental temperature: Temp.25oC (thermoneutral environment).
3) Rest: Minimum muscular activity. Very difficult for animals other than
man.
BMR is 10-15% higher when animals are standing than that of lying
down
4) Post-absorptive state: State when the process or digestion or absorption
disappears.
Overnight starvation in case of human,
Ruminants about 3-4 days
Last two conditions cannot be fulfilled for ruminant animals, hence the
term resting metabolism is used in place of basal metabolism.
Resting metabolism denotes the heat eliminated when animal is lying at
rest
8. Fasting metabolism/ Basal metabolism
• Heat production or basal metabolism rate varies with body size.
• Rubner developed the concept of surface area law
– Heat given off by is directly proportional to their body
surface.
B.M (Kcal) = 70× W 0.75 Kg
• The coefficient 70 is an average value for the Kcal of basal heat
produced per unit of metabolic size of adult mammals.
• .
9. Methods to determine the energy required for
maintenance of animals:
1) Measuring basal or fasting metabolic rate
2) Short and long term trials with mature, non producing
animals fed at the maintenance level (if the energy
content of their food is known).
3) Feeding trials with different levels of feed intakes and
by extrapolation of intake of feed towards zero level of
production.
10. Methods adopted to estimate energy requirements for maintenance
• Fasting metabolism as a basis for estimating maintenance
requirement:
• Energy expended for maintenance of an animal is converted
into heat and leaves the body.
• Dry non-producing, mature animals are fasted, kept in a
thermoneutral environment and their heat production
determined (fasting catabolism).
•
• This gives an estimate about the minimum quantity of net
nergy which must be supplied to the animal to keep it in
energy equilibrium.
• This can be estimated by both direct and indirect
11. Protein Requirements for Maintenance
• Loss of protein continuously occurs through wear and tear of body
tissue, for renewal of hairs, nails, feathers, hooves etc., which
represents the amount of protein required for maintenance.
• The losses of body protein in the animal when kept on a protein
free ration occurs through urine and faeces in negligible amount,
through shedding of hairs, loss of nail, skin etc.
• The loss, which occurs through urine, is known as EUN or
endogenous urinary nitrogen loss and loss, which occurs through
faeces, is called MFN or Metabolic faecal nitrogen loss.
12. Endogenous Nitrogen metabolism(EUN):
• Loss of nitrogen is due to the catabolism incidental to
maintenance of the vital tissues of the body, which can be
measured at the minimum urinary excretion on a nitrogen
free otherwise adequate (particularly energy adequacy) diet.
• EUN is a function of body size.
• Mammals excrete 2 mg of EUN/Kcal of basal metabolism or
140 mg N/kg0.75/day.
• EUN is highest in young animals
• EUN is lowest during hibernation.
• EUN of Indian cattle 0.2g/kg BW
13. Metabolic faecal nitrogen (MFN or FNm):
• MFN consists of spent digestive enzymes, abraded mucosa and
bacterial nitrogen.
• MFN is proportional to feed intake.
• The MFN values determined in Indian cattle were 0.35 g/100 g DMI
and in buffaloes 0.34 g/100 g DM intake.
• Endogenous urinary nitrogen and metabolic faecal nitrogen put
together has come to 350 mg N/kg metabolic body size per day in
ruminants.
• It is two to three times as great as in non-ruminants.
14. Methods adopted to estimate protein requirement for maintenance
1. Nitrogen balance method
• Various rations containing different levels of protein are
fed to the various groups of non producing adult and
healthy animals.
• The rations are otherwise adequate in energy, minerals
and vitamins required by the animals.
• Nitrogen balance is determined in the experimental
animals.
• The minimum protein intake at which nitrogen
equilibrium is achieved is the maintenance requirement.
15. Methods adopted to estimate protein requirement for maintenance
2. Feeding trial method
• Long term feeding trials are conducted with non
producing adult, healthy animals which are kept
on different levels of protein with adequate
intake of energy, minerals and vitamins.
• The level of protein at which the animal
maintains its body weight without loss or gain
over an extended period is considered the
maintenance requirement of protein.
16. Methods adopted to estimate protein requirement for maintenance
3. Factorial method
• EUN and MFN are estimated to assess protein
requirement. Dermal losses of hair and scuff
(2.2g N/d) are also included.
• The net requirement, however only covered
replacing these losses and the efficiency with
which the absorbed protein is utilized (BV
value) also must be considered.
• BV values of 70% for cattle and 65% for sheep.
17. ESTIMATION OF ENERGY REQUIREMENT FOR
GROWTH AND FATTENING
• Growth is the increase in weight and or size that occurs over time
• Energy requirement for growth and fattening can be obtained by
1) Factorial calculations
2) Feeding trials
Factorial calculations
• The principle of energy requirement for growth is that the energy of the tissue
formed is determined first and the value of basal metabolism increased by an
activity factor is added to it.
• Thus the requirement of energy is determined at any given period by the expected
rate of gain and the average body weight during the period in question.
• Data from the slaughter experiment in respect of the fat and protein provides the
figure for computing the calories for expected rate of gain while the body weight
data provide the basis for arriving at the required energy for basal metabolism.
• An activity increment over the energy required for basal metabolism has to be
considered.
• The data of basal metabolism and activity factor is to cover the maintenance
requirement.
18. ESTIMATION OF Protein REQUIREMENT FOR GROWTH
1. Nitrogen balance studies
• It is an exact measure of actual requirement of protein.
• Calves are raised on equal amounts of dry matter and on
isocaloric rations which contain different levels of protein
and the minimum intake of protein which provides
maximum retention is taken as the estimate of
requirement.
Disadvantages
● It is a short-term measurement carried out under
closely controlled conditions and thus question
always arises as to how accurately the results apply
to the long-term feeding.
19. ESTIMATION OF Protein REQUIREMENT FOR GROWTH
2. Feeding trials
• The rations containing different levels of
protein are fed to determine the minimum
level required to give the maximum rate of
growth.
• The nature of growth thus obtained may be
further tested by slaughter tests for assessing
the integrity of the nitrogenous tissues.
20. ESTIMATION OF Protein REQUIREMENT FOR GROWTH
3. Factorial method
• The amount of protein required for maintenance is
determined first.
• The value thus obtained is added to the amount of protein
required for growth (or say gain in weight) plus losses in
metabolism.
• The maintenance needs can be determined directly on the
basis of endogenous urinary nitrogen or calculated from
the basal energy metabolism and later corrected for
metabolic faecal nitrogen losses. The amount required for
the growth tissue formed can be estimated from the
slaughter data.
