
NITROGENOUS FEEDING STUFES. 87 
repair as it is being constantly worn out; and (2) to yield 
energy in the form of heat to keep the body warm, and in the 
form of power for the work it has to perform. ‘The chief 
building materials of the food are the protein or nitrogenous 
compounds. ‘These build up and repair the nitrogenous tis- 
sues, as the muscle and bone, and supply the albuminoids of the 
milk and other fluids. ‘The chief fuel ingredients of the food 
are the carbohydrates, such as sugar, starch and fiber, and 
the fats and oils. These are either consumed in the body to 
produce heat and muscular power or are stored up as fat. 
fuel Value.—The value of food as fuel may be measured 
by the amount of energy capable of being-transformed into 
heat within the body. The unit of measure commonly used 
is the calorie. One calorie is approximately the amount of 
heat necessary to raise the temperature of a pound of water 
four degrees Fahrenheit. From experiment it has been esti- 
mated that a pound of protein or carbohydrates when burned 
in the body yields energy corresponding to about 1,860 calories; 
and a pound of fat about 4,220 calories. 
food for Maintenance and for Production.—The body requires 
a certain amount of food for maintenance. When a horse or a 
cow is at rest in the stall it is continually using its muscles and 
other tissues for respiration, for keeping the blood in circulation, 
aud for other work within the body. In these ways the animal 
machinery is being constantly worn out and must be kept in 
repair. For this repair, this making up for constant waste, a 
certain amount of food is needed. The muscular work also 
requires power. ‘The power comes from the burning of the 
food just as truly as the power that moves the locomotive 
comes from the coal that is burned in the furnace. ‘The ani- 
mal machine differs from the locomotive, however; in that it 
uses its own substance for fuel. But the material thus used 
must, of course, be replaced. The amount of building material 
needed to make up for the constant wear and tear of the ani- 
mal machine is much larger than is the case with the locomo- 
tive. Finally, the body must be kept warm. ‘This requires 
fuel also, and here again the food is the fuel. 
If the horse is drawing a load it needs more food than if 
it is standing in the stable. It must have more protein to 
make up for the increased wear of the machinery, especially if 
