USES OF FEED BY ANIMALS FEEDING STANDARDS 49 



of fat, and one pound of digestible fat, .474 to .598 pound body fat. 



Functions of Fat. The fat in feeds serves a similar purpose in 

 animal nutrition as the carbohydrates, viz., to supply energy for the 

 maintenance of body heat, for the production of work and for the 

 formation of body fat. Since the fats contain a smaller percentage 

 of oxygen than the carbohydrates, with a larger proportion of 

 carbon and hydrogen to yield energy upon oxidation in the animal 

 body, they are a more concentrated and valuable feed component 

 than the carbohydrates. Direct experiments have shown that pure 

 fats yield close to two and one-fourth times as much heat on com- 

 plete oxidation as do starch and other carbohydrates ; it is cus- 

 tomary, therefore, in considering the non-nitrogenous organic com- 

 ponents as a group, to reduce the fat to its starch equivalent by 

 multiplying with two and one-fourth (p. 38). Fat is ordinarily 

 present in only relatively small amounts in feeding stuffs, except in 

 oil-bearing seeds and some factory by-products, and it is not, there- 

 fore, of the importance in the feeding of farm animals as the carbo- 

 hydrates, but in addition to furnishing a concentrated feed ma- 

 terial it serves very useful purposes in rendering feeds palatable to 

 stock and regulating bowel action. 



Wihen the digested 'and absorbed fat is not used for the produc- 

 tion of heat or muscular energy, it may be deposited as 1 body fat. 

 According to Kellner, the amount of body fat that may be formed 

 from 100 pounds of digestible fat in the feed, is lower in the case of 

 herbivora than that of carnivora, and varies from about 64 pounds 

 of pure fats (oil) to 47 pounds for fats in coarse feeds. 



There is considerable evidence that fat in the feed may be ab- 

 sorbed in the body in the form of emulsion without being decomposed 

 into free fatty acids and glycerin; this view is supported by the 

 fact that certain components of fats, like cottonseed oil or sesame 

 oil, may be identified in the body fat of animals receiving these in 

 their feed, through characteristic chemical tests, and the body fat, 

 or that in the milk, in the case of heavy feeding of fats, often par- 

 take of the characteristic properties of these feeds, e.g., cottonseed 

 meal produces a hard, tallowy butter and pork of .similar character ; 

 acorns, on the other hand, produce a soft, oily pork; a number of 

 other feeds have a marked influence on the chemical or physical 

 properties of the fat produced. 



Muscular Energy. One of the problems connected with feed- 

 ing of farm animals concerning which men of science have held 

 divergent views, is that relating to the source of muscular energy. 

 Since animals 'accomplish the work done by exercise of their 

 muscles, which are composed largely of protein substances, it might 

 be supposed that severe work would greatly increase the oxidation 



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