ANN 121: Applied Animal Nutrition-I (2+1)

ESTIMATION OF  ENERGY REQUIREMENT FOR GROWTH AND FATTENING

• Energy requirement for growth and fattening can be obtained by 
  • Factorial calculations and 
  • 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.
• Thus the sum of calories of basal metabolism + activity increment factor + growth tissue formed is the estimated energy requirement expressed as net energy.

70% DE = NE,

80% DE = ME,

1 Kg TDN = 4.4. MCal. DE

Based on feeding trials

• Feeding different groups of animals with different levels of energy and determining the energy level that promotes the growth or fattening. Much of the earlier recommendations for beef and dairy cattle, swine and sheep were on this basis.
• The energy requirements of growing and fattening swine in current NRC standards (1998) were based on feeding trials.
• Although these were expressed in terms of DE and ME, some of the values were converted from TDN.
• The ME was appoximated as 96% of the DE values in pigs and 82% in dairy cattle.