Methods adopted for assessing energy and protein requirement in Livestock

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
• Quantity of nutrients 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 body
composition remains constant .
• An animal 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. 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.

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 has been adequate
2) Environmental temperature: Temp.25oC (thermoneutral).
3) Rest: Minimum muscular activity.
~ Very difficult for animals other than man.
~ BMR is 10-15% higher in standing animals 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 ruminants, hence the term
Fasting metabolism is used in place of basal metabolism.

8. 1. Fasting metabolism :
• 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 is the minimum quantity of net energy which must be
supplied to the animal to keep it in energy equilibrium.
• This can be estimated by both direct and indirect
calorimetry.

9. 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.

10. Methods to determine the energy required for
maintenance of animals:
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).
Constant (No Change in) body weight-
Zero balance
Energy Equilibrium of Animal~ zero balance

11. Methods to determine the energy required for
maintenance of animals:
3. Feeding trials with different levels of feed intakes and by
extrapolation of intake of feed towards zero level of
production.
Regression methods:
 Body weight change due to varying amount of dietary energy
 Dietary energy intake at which body weight change is zero

12. 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.

13. 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

14. 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.

15. 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.

16. 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.

17. 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.

18. ENERGY REQUIREMENT FOR GROWTH
• 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

19. ENERGY REQUIREMENT FOR GROWTH
1. Factorial calculations
• Energy of the tissue formed is determined first.
– Data from the slaughter experiment in respect of the fat and protein
provides the figure for computing the calories for expected rate of gain.
• Value of basal metabolism is added.
• Thus the sum of calories of basal metabolism + activity
increment factor + growth tissue formed is the estimated energy
requirement expressed as net energy.

20. ENERGY REQUIREMENT FOR GROWTH
2. Feeding trial method
• Feeding different groups of animals with different
levels of energy and determining the energy level
that promotes the growth

21. PROTEIN REQUIREMENT FOR GROWTH
• Protein requirement for growth and fattening can be
obtained by
1) Nitrogen balance studies
2) Factorial calculations
3) Feeding trials

22. ESTIMATION OF Protein REQUIREMENT FOR GROWTH
1. Nitrogen balance studies
• Various levels of protein are fed to animals and the lowest
levels 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.

23. 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.

24. 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 WEIGHT gain plus losses in metabolism.
•
• The amount required for the growth tissue formed can be
estimated from the slaughter data.

25. Energy & Protein Requirement for Milk
• Energy requirement of milk production are based on:
– Composition of the milk
– Milk yield
– Efficiency of conversion of dietary energy into milk energy
• Milk yields are adjusted to a 4% fat equivalent
• Gaines Formula for 4% fat corrected milk (FCM)
FCM (kg) = (0.4 + 0.15F) X M
Where, F = Fat % in the milk M = Quantity of milk produced/day
• Energy Requirement:
NE (kcal)= 750x FCM (kg); TDN (kg)= 0.335 x FCM (kg)
• Protein Requirement:
• DCP (gram)= 55 x FCM (kg)

27. mals excrete 2 mg of EUN/Kcal of basal metabolism or 140 mg
0.75/day.