CHAPTER V 



FUNCTIONS OF THE FEED NUTRIENTS IN THE 

 ANIMAL BODY 



In describing the digestion and absorption of the feed 

 nutrients thus far, we have not found them to be of any nu- 

 tritive value to the animal body. However, after digestion 

 and absorption, the nutrients are ready for distribution by 

 the blood for the utiUzation of the different tissues of the 

 body for various purposes. 



Metabolism. — The sum of all the changes which the 

 absorbed food undergoes in the body is known as me- 

 tabolism. The term meta])olism includes all the changes 

 and transformations which the digested nutrients undergo 

 from the time they are absorbed until they are finally excreted 

 from the body. It covers all the chemical changes in the 

 animal body which constitute the hfe of the animal. Thus, 

 the repair of body tissue, growth, the storage of fat, and the 

 production of milk are all included in the processes of me- 

 taboUsm. On the other hand, the breaking down of the pro- 

 tein tissues and the oxidation of fat and carbohydrates for 

 the hberation of their energy are also included in the meta- 

 bolic processes. Thus the functions of the digested and ab- 

 sorbed nutrients of the feed are all included under the term, 

 metabolism. 



In general, animals use food in three ways: (1) for the 

 formation, growth, and repair of the muscles, bones, ten- 



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