FEED NUTRIENTS IN THE ANIMAL BODY 80 



The different kinds of carbohj^drates have different values 

 for fat production. Thus 100 pounds of digestible starch 

 or crude fiber fed above the maintenance requirement of 

 the animal may produce about 25 pounds of body fat, while 

 the same amount of digestible cane sugar may produce only 

 19 pounds of fat. According to Kellner/ protein and car- 

 bohydrates have about the same values as fat producers. 



Functions of Fat. — The functions of the fat of the feed 

 are: (1) to serve as fuel for the liberation of energy; and 

 (2) to serve as a source of the body fat. 



The absorbed fat is carried by the blood to the muscular 

 tissues, where it may be oxidized immediately for the Ubera- 

 tion of energy. The end products of the oxidation are car- 

 bon dioxide and water. The carbon dioxide is excreted 

 mainly through the lungs, and the water is excreted mainly 

 through the urine. 



Any excess of fat above the needs of the body for the produc- 

 tion of energy may be stored in the cells of the tissues as body 

 fat. The body fat acts as a reserve food supply which may 

 be called upon to furnish energy to the animal body at any 

 time when the ration is insufficient to supply its demands. 



One hundred pounds of digestible fat in the ration above 

 the requirements of the animal for maintenance may form 

 from 47 to 60 pounds of body fat. In general, fat is about 

 2i times as valuable for the production of body fat as the 

 same amount of protein or carbohydrates. 



The Nutritive Ratio. — Inasmuch as it is very difficult 

 to remember even approximately the relative amounts of 

 digestil)le nutrients in the feedingstuffs, scientists have 

 endeavored to simplify it l^y introducing the term, nutritive 



* "The Scientific Feeding of Animals," p. 75. 



