How Caffle Foods Differ 249 



are, however, certain chemical differences among the 

 various groups of feeding stuffs, a knowledge of which is 

 helpful in selecting materials for compounding rations. 



Coarse foods vs. grains and grain products. — In com- 

 paring hays, straws, and other fodders with grains 

 and grain products there are points of chemical uu- 

 likeness which bear an important relation to problems 

 of nutrition. In the first place, the nitrogen com- 

 pounds differ. In the grains we find the nitrogen 

 combined mostly in the form of albuminoids, while in 

 the fodders a proportion of it, and sometimes quite a 

 large one, exists iu amides. This is a point in favor 

 of the grains, for, as we have seen, the nutritive 

 function of amides is probabh' more limited than that 

 of albuminoids. Again, the non-nitrogenous material 

 of the grains is in general superior to that of the her- 

 baceous cattle foods. In the former, especially in the 

 cereal grains, there is but little fiber and the nitrogen - 

 free extract is made up largely of starch and other 

 bodies, whose net value in nourishing an animal is 

 quite surely greater than that of fiber and gums found 

 in such abundance in the hays and otlier fodders. 

 The work of digesting fiber and gums is greater than 

 with sugar or starch, and of the digested material from 

 the former we cannot affirm an equal value with that 

 coming from the more easily soluble carbohydrates. 

 In short, the terms protein and nitrogen -free extract 

 do not signify the same compounds or the same values 

 when applied to different feeding stuffs. 



Classification according to tlie proportions of nu- 

 trients . — The relative proportion of nitrogenous and 



