FEED NUTRIENTS IN THE ANIMAL BODY 11 



dons, skin, hair, hoof, horn, and of the various organs, 

 mem])ranes, and secretions ; (2) as fuel for the hberation of 

 energy to produce work or heat ; (3) for the formation of 

 body fat ; and (4) for the formation of body glycogen. 



Functions of Water. — The importance of water to the 

 animal organism is shown by the fact that ordinarily from 

 one-third to two-thirds of the weight of the animal body 

 consists of water. Water is necessary to the life of every 

 cell. It acts as a solvent for various substances, it is a 

 carrier of nourishment to the cells, and it removes waste 

 products away from the cells. It often assists in cooling 

 the body by evaporation from the skin as perspiration. It 

 is necessary also for many important chemical reactions 

 which take place in the animal body. Water ordinarily is 

 excreted from the body, principally in the urine, and to a 

 slight extent in the perspiration, feces, and water vapor 

 from the lungs. 



Functions of Mineral Matter. — It was noted under the 

 discussion of the chemical composition of the animal body 

 that from 3 to 6 per cent of the body is composed of mineral 

 matter. The skeleton, especially, the protein tissues, the 

 blood, and the body fluids all contain a certain amount of 

 mineral matter. 



Thus, the mineral matter of the feed is used for the forma- 

 tion and repair of the bones, the protein tissues, and the body 

 fluids, such as the blood, the milk, and the digestive fluids. 

 The mineral matter is also used to maintain the neutraUty, 

 alkalinity, or acidity, as the case may be, of the fluids and 

 tissues of the body. It has no value for the production of 

 fat or for the liberation of energy. Mineral matter is ex- 

 creted from the body in the feces, urine, and, to a sHght 



