136 Bulletin 154. 



stances occur in the animal body in somewhat varying propor- 

 tions, depending upon age, condition, treatment, etc. 



Water is an essential constituent of the animal body and 

 constitutes from 40 to 60 per cent of its live weight. Ash occurs 

 mainly in the bones and constitutes from two to five per cent of 

 the live weight. The fat occurs in greatly varying proportions, 

 but rarely is less than six or more than thirt}^ per cent. All 

 those substances containing nitrogen are classed as protein. 

 The}'^ constitute an important group of which washed lean meat 

 and the white of egg msLY be taken as tj'^pes. They contain 

 about 16 per cent of the element nitrogen and are the only class 

 into the composition of which this element enters. All the work- 

 ing machiner}' of the body, such as flesh, skin, bones, hair, 

 internal organs, brain and nerves, contain a large proportion of 

 protein. 



Com POSIT lox of Food Materials. 



The same four groups of substances found in animal bodies, 

 viz.: water, ash, fat and protein, are also found in the food they 

 consume and in addition the food of herbivorous animals contains 

 a class called carbohydrates. 



Water. — All food stuffs, no matter how dry the^^ may seem, 

 contain a considerable amount of water. In grains and dried 

 fodders it ranges from 8 to 15 per cent of the material, in green 

 forage and silage it is about 80 per cent, while in some roots it 

 amounts to 90 percent. While water is essential to animal life 

 and the water in the food fulfills the same function as that drunk 

 by the animal, we do not value food materials for the water they 

 contain, and computions are based upon the water-free or dry 

 matter. 



Ash. — When a food stuff is burned till the organic matter is all 

 driven off the residue is the ash. It is composed largely of lime, 

 magnesia, potash, soda, iron, chlorine, and carbonic, sulfuric and 

 phosphoric acids. The ash of the food is the source of the min- 

 eral matter of the animal body and as such is of great importance. 

 Ordinary combinations of feeding stuffs, however, contain an 

 abundant supply of mineral matter for the use of the animal, so 



