Methods of assessing the energy values of foods for ruminant animals.

Assessment of energy value of foods 131 of the same species? Two world wars have forced us to think of human beings and of farm animals as populations in a statistical sense. We count heads, assign ‘man values’ for energy requirements. Such a practice is essential for the administrator, but it does ignore individual differences. We have no evidence for variation in the efficiency of the fundamental biochemical processes with which individuals of the same species liberate energy from food. Yet human beings, as individuals, do differ in their instinctive demand for food. This difference is not necessarily correlated with the expenditure of energy. The obese human being within the nation is an inefficient individual. But the ox, fattening in his stall, is fulfilling his man-made destiny. The assessment of the energy value of human and animal foods cannot then be studied as a problem in pure chemistry. In due time biochemistry will elucidate the complexities of the processes at molecular and cellular level which determine the liberation of energy from food. But the final word is with the living animal itself which is a biological entity. And a human being is also a person.