198 The Feeding of Animals 



DETERMINATION OF ENERGY VALUES 



We have reached a point in our study of animal 

 nutrition where we realize that food values are to 

 some extent commensurable with energy values and 

 that it is desirable to know the energy product of 

 different compounds and feeding stuffs. Moreover, we 

 cannot possess sufficiently full knowledge concerning 

 the energy needs of the several classes of animals 

 until we have measured energy consumption under 

 the various conditions of work and of production. 

 The mere determination of the income and outgo of 

 the animal body does not necessarily measure energy 

 needs or use. We may go so far as to ascertain that 

 a certain amount of carbon from a certain source 

 was consumed in a given time, but from this alone we 

 do not learn the extent to which this combustion has 

 supported the internal and external work of the body. 



Calculation of the energy value of a ration. — Three 

 methods may be adopted for determining the energy 

 expenditure by an animal eating a given ration. The 

 one of these most easilj" carried out is largely a 

 matter of mathematical calculation. By the use of 

 average digestion coefficients it is possible to ascer- 

 tain approximately the amounts of digestible protein, 

 carbohydrates and fats contained in any ration which 

 is apparently accomplishing a desired result. We know 

 from previous determinations what are the calorific 

 values of individual compounds such as albumin, 

 starch, sugar, stearin and olein, and these compounds 

 are assumed to represent the energy value of the 



