38 MANUAL OF FABM ANIMALS 



form. The animal must maintain its existence, and for this 

 both energy and matter are required. A large part of the energy 

 of the food goes to the maintenance of the body temperature. 

 The body temperature of farm animals is considerably above that 

 of the surrounding atmosphere, and its maintenance requires 

 much heat, as the body is continually giving off heat. The 

 body tissues become worn out and must be constantly renewed. 

 This must be supplied by the matter and energy from the food. 

 In the case of young animals, there is a constant formation of 

 new tissue. This requires more matter than energy. Again, the 

 muscular function of vital processes require much energy, which 

 must be supplied by the food. Of the total amount of food 

 that an animal will ordinarily consume, a very large proportion 

 goes to support life and a small amount to production. 



Composition of food. — The value of a food depends, among 

 other things, on its composition. There is a tendency to ig- 

 nore the fact that a food should be considered with reference to 

 its composition. It is assumed that a pound of timothy hay, 

 for example, is equivalent to a pound of clover hay, when as a 

 matter of fact their composition is such as to make them widely 

 different, so that one will not take the place of the other. The 

 number of compounds found in the food is very large, and many 

 of them very complex in their nature. For convenience in 

 comparing foods, these compounds are grouped into classes. 

 These classes are few in number, easy to comprehend, and serve 

 the purpose well from a practical point of view. We recognize 

 five distinct groups, one of which is divided into two sub-groups. 

 They are as follows : — 



1. Water 



2. Ash (mineral compounds) 



3. Protein (nitrogenous compounds) 



4. Carbohydrates |§I^,te'^.?Jee extract '"^'™"*^ 



5. Fats 



Dry- 

 matter 



It is customary to group together all the substances of a food 



