DIGESTIBILITY OF FEEDS 



287 



cellulose is a less efficient one. 1 The carbohydrates form 

 only a very small proportion of the body, less than 1 

 per cent. Their chief function is to furnish energy for 

 keeping the body warm and for movement. They are 

 also important as a source of animal fat. The animal can 

 change the carbohydrates to fat, and the body fat can 

 be used as a source of energy when the food does not 

 supply enough. The fat is a reserve source of energy. 



DIGESTIBILITY OF FEEDS 



263. Feeds Differ in Digestibility. No feed can be entirely 

 digested. A part of the food material is never taken up 

 by the body. The proportion of digestible material is 

 quite different in different food materials. The propor- 

 tion also varies with the kind of animal and with the 

 particular individual. The ruminants, or cud-chewing 

 animals, cattle, sheep and goats, all digest their food 

 about equally well. Horses digest 11 to 12 per cent less 

 than ruminants. 



AVERAGE DIGESTIBILITY FOR RUMINANTS 



1 The carbohydrates contain carbon, hydrogen and oxygen. The pro- 

 portions of hydrogen and oxygen are the same as in water (HjO), hence 

 the name. That is, there are two atoms of hydrogen for each atom of 

 oxygen. There are a large number of different carbohydrate compounds. 

 The composition of starch is CgHj.jO,,, of cane sugar C^H^On. of grape 

 sugar or glucose C,H 12 O 9 . 



