CHEMISTRY OF THE FEEDING OF ANIMALS. 185 



proportion of indigestible matter than that of sheep, and that of 

 eheep more than that of pigs. 



5. That oxen require from 5 to 6, and sheep from 3 to 4 times 

 as much time to add a given proportion to the weight of their 

 bodies as pigs. 



6. That the greater portion of the nitrogenous and mineral mat- 

 ters of the food is recovered in the manure ; and that the greater 

 part of the non-nitrogenous substance is lost by respiration and 

 other exhalations— a much smaller proportion being retained in 

 the increase, or voided in the manure. 



T. That for a given amount of increase produced, oxen void 

 considerably more substance as manure, and expend more in res- 

 piration, &c., than sheep, and sheep very much more than pigs. 



8. That for a given weight of dry substance consumed, oxen 

 void more as manure than sheep, and sheep much more than pigs ; 

 but oxen respire rather less than sheep, and sheep rather less than 

 pigs. 



9. That in proportion to a given weight of animal, within a 

 given time, oxen both consume and respire less dry substance of 

 food than sheep, and sheep very much less than pigs ; but they 

 void almost identical amounts of dry substance as manure. 



Camparative Feeding Value of different Foods, according to their 



Composition. 



Thus far I have endeavored to indicate the characteristic points 

 of distinction between the food of the ox, the sheep, and the pig, 

 and to show in what respects its constituents are differently dis- 

 posed of by the different animals ; and for the purposes of my 

 illustration, I have supposed the animals to be fed on such foods 

 as are recognized as appropriate to them, and in such proportion 

 and amount as experience justifies. I now propose to say a few 

 words on the relative feeding properties of different foods, ac- 

 cording to their composition. 



Leaving out of view, just now, the incombustible or mineral 

 constituents, it will be convenient, as before, to consider the 

 other constituents of food to be grouped under the heads of nitro- 

 genous and non-nitrogenous substances. 



Among the nitrogenous substances, the most important of those 

 Which enter into our stock foods are albumen, casein, legumin, 

 and gluten ; and chemists and physiologists are accustomed to 



