Computing Rations for Farm Animals. 137 



it is not a matter of practical concern except as it has a bearing 

 on the mineral elements of fertility in the manure. 



Fats. — This group embraces the materials which may be dis- 

 solved from a feeding stuff by either. ' It includes, besides the 

 true fats, wax and coloring matter. Fat in the food may be either 

 stored in the body as fat, or burned to produce heat and energy. 



Carbohydrates. — This term includes two groups, nitrogen-free 

 extract, such as starch, sugar, gum, etc., and fiber or the woody 

 part of plants. The former are quite freely digested, the latter 

 much less so, though fulfilling the same function to the extent it 

 is digested. The carbohydrates constitute the largest part of 

 vegetable foods. They are not stored in the animal body as 

 such, but are converted into fat or used (burned) to produce heat 

 and energy. 



Since the car boh3^drates and fat serve nearly the same purpose 

 in the animal economy, they may, for convenience, be grouped 

 together. Experiments, however, have shown that fat is about 

 2^ times as effective as a food as are the carbohydrates. Hence 

 it is customary to multiply the amount of fat by 2^ to reduce it 

 to a " starch equivalent " before adding it to the amount of the 

 carbohydrates. 



Protein. — The protein of foods, like that of the animal body 

 is characterized by containg nitrogen. It therefore, is fre- 

 quently termed " 7iitrogenousvoi2i\X^x.'" The iQxm. albiunenoids is 

 sometimes used to designate this group, though it more correctly 

 implies a certain class of protein substances. The function of 

 protein in the food is, first of all, to build up and repair the 

 working machiner}^ of the body, and to supph^ protein for the 

 production of milk, wool, etc. For no other food constituent can 

 fulfill this function. 



The importance of a sufficient supply of protein in the ration 

 is, therefore, apparent. If in excess of the amount required to 

 build up and repair the waste of the body the protein may be 

 converted into fat and deposited as such or used to produce heat 

 and energy. Its efficiency for these purposes is about the same 

 as the carbohydrates, but as it is usually far more expensive to 

 supply than the carbohydrates, economy would dictate that only 

 so much should be supplied to the animal as will suffice to repair 



