126 SWIKE 



amount of soy-beans in the ration, and the difference di- 

 vided by the total amount fed, which is supposed to give 

 the coefficient of digestibility for soy-beans. While in 

 some cases this may be accurate, it is usually inaccurate. 



Recent experiments by the writer have shown that 

 combinations of feeds in general are digested much more 

 thoroughly than single feeds, the difference being so great 

 that the coefficients of digestibility for some of the 

 nutrients of nitrogenous concentrates is far greater than 

 100 per cent, indicating that the supplemental feed exer- 

 cises a favorable influence upon the extent to which the 

 basal ration is digested. With this in view, it is obvious 

 that the coefficients of digestibility for the nutrients of 

 the feeds that are determined by calculation are not ac- 

 curate; furthermore, where the coefficients for a single 

 feed have been determined directly, they are not as high 

 as when used in combination with other feeds. 



By using several different kinds of concentrated feeds 

 in various proportions it was shown that the coefficient 

 of digestibility for carbohydrate is practically constant, 

 and that a pig digests 90 per cent of this nutrient. The 

 coefficients for the other nutrients vary considerably. 

 Crude protein ranges from 67 to 85 per cent and ether ex- 

 tract from 60 to 90 per cent. Thus it is seen that the di- 

 gestible nutrients given in the succeeding tables, since 

 they are made up from average coefficients of digesti- 

 bility, may not be absolutely accurate, but they are the 

 best available. Furthermore, as determined by the writer, 

 these are much more nearly accurate than many other 

 conditions of a practical nature that determine results in 

 swine feeding. 



Protein. — Protein is the general name for the nitrog- 

 enous compounds that are used by the animal body for 



