306 MANUAL OF CATTLE-FEEDING. 



losses from tlie body, as well as the supply of material for 

 new growth, is accomplished by means of the food. 



Plainly, however, it is not the food as a whole, but 

 those ingredients of it which are digested which can serve 

 this purpose. Neglecting, as before, water and ash, the 

 substances digested an*d resorbed from the food are essen- 

 tially three in number, viz., protein, fat, and carbhydrates ; 

 and it is with these three kinds of matter that the amount 

 of protein and fat in the body is maintained or increased. 

 The digested protein of the food is the sole source of the 

 protein of the body, while, as we have seen, the investi- 

 gations thus far made lead us to the conclusion that all 

 three groups.of nutrients probably contribute to the forma- 

 tion of fat. 



Feeding Standards.— In the last three chapters of Part 

 I. we took up tbe general laws regulating the production 

 of flesh, fat, and work in the body. It became evident 

 from the considerations there presented (compare page J 1)6) 

 that an essentially different proportion of nitrogenous and 

 non-nitrogenous nutrients is reqliired in the fodder accord- 

 ing to the object of the feeding, a conclusion which is 

 plainly in harmony with practical experience. 



The chief object of invcKstigation in the field of cattle- 

 feeding was there stated to be the determination of the 

 quantity and proportions of the several nutrients reriuired 

 in the fodder of animals kept for various purposes. The 

 results of such investigation are concisely expressed in 

 what are called "Feeding Standards," which are simply 

 statements of the amounts of digestible protein, carbhy- 

 drates, and fat, which experience has shown to l)e in gen- 

 eral best adapted to the purpose in view. For examph*, 

 the feeding standard for milk cows given by Wolff is as 

 follows : 



