THE FEEDING OF ANIMALS 47 



food, the composition of which has been previously determined 

 by a chemist. Provision is then made for collecting all excreta. 

 By making an analysis of this waste matter, the undigested 

 protein, carbohydrates, and fat are found. This, deducted from 

 the total in the food, gives the digested part. The amount of 

 each constituent digested divided by the total in the food gives 

 the percentage digestible. This is called the "coefficient of digesti- 

 bility." The grains are more highly digestible than the coarse 

 fodders; for example, in corn the protein is 76 per cent digestible, 

 the crude fiber 58, the nitrogen-free extract 93, and the fat 86 

 per cent digestible, while in timothy hay the protein is 56 per 

 cent, the crude fiber 58, the nitrogen-free extract 63, and the fat 

 57 per cent digestible. 



Among the various food materials the carbohydrates as a 

 rule are the most digestible, running as high as 95 per cent in case 

 of corn, while the crude fiber is the least digestible, and between 

 these lie fat and protein. In general the fat is more digestible 

 than the protein. As a rule, the digestible coefficient falls 

 when large amounts of foods are used. If we crowd the con- 

 sumption of food, the animal does not digest it as thoroughly as 

 it would if fed smaller amounts. On the other hand, we cannot 

 secure a greater digestibility by limiting the consumption. 

 Animals under a starving ration do not digest any more than 

 when fed a normal amount. 



Having the composition of the food as determined by the 

 chemist, and the digestible coefficient as determined with the 

 animal, it is an easy matter to calculate the amount of digestible 

 nutrients in the various food-stuffs. It is with the digestible 

 nutrients, and not the total food materials, that the feeder is 

 concerned in choosing a ration. A great deal of work has been 

 done at the various experiment stations to determine the digesti- 

 bility of food-stuffs. For ready reference Table II, showing the 

 amount of digestible nutrients in a large number of foods, is 

 pubUshed in the Appendix of this manual. 



