18 AGRICULTURAL EXPERIMENT STATION. [Jan. 



as other carbohydrates. The elementary composition of the 

 extract matter is carbon, oxygen and hydrogen. 



Functions of the Extract Matter. — The sugars, starch 

 and gums furnish energy, and serve as sources of fat. The 

 crude cellulose and the extract matter, having the same 

 functions in the animal economy, namely, the production of 

 energy and fat, have been termed carbohydrates. The ash, 

 while a necessary ingredient of all complete foods for live 

 stock, is not generally considered in compounding suitable 

 daily diets for our farm animals ; so that, for practical pur- 

 poses, we really have to do with but three groups: (1) 

 protein, (2) carbohydrates, (3) fat. 



Having noted the different groups of substances of which 

 our agricultural plants are composed, let us briefly turn our 

 attention to the value of these groups as sources of nourish- 

 ment. No one of them is of itself a suitable food for our 

 farm animals, nor will any one of them sustain life for any 

 lenn-th of time. 



Digestibility of Cattle Foods. 



Foods are valuable as sources of nourishment only in so 

 far as their various constituents or groups can be digested 

 and assimilated. Two kinds of hay, one early and the other 

 late cut, might be consumed in equal quantities by an 

 animal, yet the early cut hay, having more digestible mat- 

 ter, would prove the more valuable fodder. In order to 

 combine the various fodders into what has been termed a 

 fodder ration, it is important to know how large a part 

 or per cent, of the various groups is digestible. A great 

 many digestion experiments have been made with various 

 cattle foods, especially in Germany ; during the last six or 

 seven years a considerable number have been carried out in 

 the United States. A tabulated list of all American experi- 

 ments will be found at the end of this report. 



How the Digestible Matter of a Food is determined. 



First ascertain the amount and composition of the food 

 consumed by an animal in a given length of time, also the 

 amount and composition of the fteces or undigested portion 



