ARID AGRICULTURE. 



317 



treated as a separate class in compounding a food 

 ration. The fats are dissolved by the chemist 

 with ether, which also dissolves some other sub- 

 stances, so they are put together in our tables 

 under the name of ether extract. 



HOW THE J n general the nitrogen substances are used 



FOODS ABE . , , , 



USED m processes of growth, to lay on muscle or in- 



crease in size, so larger amounts of them are 

 used in rations for young, growing animals, or 

 for breeding animals, or cows giving large 

 amounts of milk which is rich in nitrogen. The 

 carbo-hydrates produce energy, as work and heat, 

 and the fats both help to lay on fat and produce 

 heat. But the complete function of the classes 

 of food can by no means be so simply stated. 



Many have the idea that a fattening ration 

 should be especially rich in fat, but that does not 

 follow. It is known that the animal body may 

 break down and change the compounds, even con- 

 verting one into the other. Protein may yield 

 fat and heat, or the carbo-hydrates may be, and 

 are largely, used to store up fat in the body. The 

 feeder needs to supply his animals with each 

 kind of food in the proportion best adapted to 

 the kind of animal for the kind of results sought. 



DETERMINED Xhe amount of different foods given to ani- 



BY EXPERT- , T . i T ,. L -i i i 1 .L 



MEITT mals which may be digested and used is deter- 



mined by experiment, and we have only these 

 actual feeding trials, along with the analyses of 



