160 THE FEEDING OF ANIMALS 



nitrogenous, the greater part of the protein eaten is not 

 stored but, excepting the nitrogen compounds of the 

 urine, is used as fuel. With milch cows or young animals 

 growing vigorously a much larger proportion escapes 

 oxidation. The fuel value of protein will be discussed 

 later under another head. 



FUNCTIONS OF CABBOHTDBATES 



232. Carbohydrates the chief source of energy. — 



Carbohydrates are usually characterized as the fuel portion 

 of the food, or that part which is oxidized to produce the 

 various forms of energy. This conception of the function 

 of these bodies is correct in the sense that in the case of 

 farm animals they constitute the larger part of the fuel, 

 although not the whole of it. 



233. Proportion of ration used as fuel. — For instance, 

 in the case of a cow eating daily sixteen pounds of diges- 

 tible organic matter, giving thirty poimds of milk con- 

 taining 15 per cent of solids, and neither gaining nor 

 losing flesh, not far from five pounds of this organic 

 matter would be foimd in the milk and urine, leaving 

 about eleven pounds to be used as fuel, about a poimd 

 and a half of which might be derived from the protein 

 and fat, the remainder, or nine and one-half pounds, con- 

 sisting of carbohydrates. -If a fattening steer were eating 

 the same amount of the same kind of food and gaining 

 two pounds of live weight daily, the body increase and 

 urine would contain not over two and one-half pounds of 

 dry matter, leaving not less than thirteen and one-half 

 pounds to be oxidized, of which twelve pounds might 

 consist of carbohydrates and fat, mostly the former. It 

 is clear, then, that while other bodies serve as fuel, the 



