Principles of Feeding 63 
to determine the digestibility of food-stuffs. For ready reference 
Table 6, showing the amount of digestible nutrients in a large 
number of foods, is published in the Appendix. 
117. Digestibility of food materials. — 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 consumption 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 limit- 
ing the consumption. Animals under a starving ration do not 
digest any more than when fed a normal amount. 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.., 
MAINTENANCE RATIONS AND PRODUCTIVE RATIONS 
A ration may be defined as the quantity of food that is con- 
sumed by an animal weighing one thousand pounds in twenty- 
four hours. In forming rations, it is necessary to take into ac- 
count the purpose for which the animal is used. For convenience 
of study, rations are divided into two general classes, — rations 
for maintenance and rations for production. 
118. Maintenance rations. — A maintenance ration is one that 
supplies the needs of a resting animal without producing any kind 
of labor and with no loss or gain of body substance. We have 
already seen that a certain amount of the food consumed by the 
animal goes to support life, maintain body temperature, repair 
waste tissue, and to provide muscular activity of vital processes. 
