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

UNIT OF REFERENCE IN FASTING METABOLISM/ BASAL METABOLISM 

• Heat production or basal metabolism rate varies with body size. Rubner developed the concept, referred to as the surface area law that the heat given off by all warm blooded animals is directly proportional to their body surface and that, expressed on this basis, heat production is constant to body surface for all species.
• The surface area on the other hand is very difficult to measure, and methods were therefore devised for predicting it from their fractional or decimal power of body weight.
• Scientists decided to standardize the expression of fasting metabolism on ¾ power of body weight i.e., Kg. W^0.75 because of the close relationship between metabolism and metabolic body weight.
• The fasting metabolism of adult animals of various species ranging in size from rat to cow has an average value of 70 kcal per Kg. W^0.75 per day, but there are considerable variations from species to species.
• Basal metabolism of various body weights are now a days determined from the formula

B.M (Kcal) = 70W ^0.75 Kg

• The coefficient 70 represents an average value for the kilocalories of basal heat produced per unit of metabolic size in experiments with groups of adult mammals.
• It should be noted that the above formula applies only in case of adult animals whose growth is complete.