Feeding Standards 283 



rations or to the profits which may result from their 

 use. 



These standards take account of two main factors: 

 (1) the quantity of available nutrients, and (2) the 

 relative proportions of the classes of nutrients. Quan- 

 tity is an essential consideration, for it is obvious that 

 enough energy and building material must be supplied 

 to do a given work. It is also obvious that quantity 

 must be a variable factor according as the animal is 

 large or small, doing hard or light work, giving much 

 or little milk, or fattening rapidly or slowly. 



Account must be made of the proportions of the 

 nutrients, because protein, for instance, has peculiar 

 functions which other nutrients cannot exercise, and 

 less than a certain minimum of the proteids would 

 limit production by just the amount of the deficiency. 

 In order for the protein to serve its maximum useful- 

 ness its energy should not be encroached upon to fill 

 a place equally well or better taken by carbohydrates; 

 consequently, the proportion of carbohydrates must also 

 be considered. 



The relative proportion of the nutrients of a ration 

 we speak of as the nutritive ratio. By this term is 

 meant the relation in quantity of the digestible pro- 

 tein to all the other digestible organic matter reck- 

 oned in terms of carbohydrates. If we multiply the 

 quantity of fat by 2.4 we get its carbohydrate equivalent, 

 and if we add this product to the quantity of diges- 

 tible carbohydrates present we have the carbohydrate 

 value of the digestible matter other than the protein. 

 This sum divided by the number representing the pro- 



