BUSINESS METHODS IN FEEDING 127 



quantity, and comprises from 40 to 80 per cent, of 

 the gross weight. .While indispensable, it has but 

 little economic importance here. 



Ash occurs principally in the bones and consti- 

 tutes from 2 to 5 per cent, of the live weight. The 

 term is applied to the residue left after complete 

 burning. 



Protein. This is the constituent which forms 

 flesh and includes all the nutrients which contain 

 nitrogen ; albumenoids being the most important. 

 Familiar forms of this nutrient are lean meat, white 

 of the egg, and the casein of milk (curd). The 

 flesh, skin, bones (in part), vital organs, brain, 

 nerves, in fact the bodily mechanism, are made up of 

 protein diluted, so to speak, with water, supported 

 by the ash of the skeleton and rounded out with 

 fat. Protein is therefore of the utmost importance. 



Fat comprises from 6 to 30 per cent, of the live 

 weight in different classes of animals and is usually 

 well distributed in the body. It consists of carbon, 

 hydrogen and oxygen, but contains no nitrogen. 

 While not so vital to the animal life as the other 

 three constituents, it has much economic interest. 



These various substances are formed from animal, 

 vegetable, and mineral matter known as food and 

 are converted by the animal eating them into flesh, 

 fat, bone, milk, wool, and work (energy). It is of 

 interest, therefore, to consider next the composition 

 of vegetable matter, or the food of animals. 



Composition of food materials. There is a simi- 

 larity between the constituents of animals and 

 plants. The four groups of substances cited under 



