36 PRINCIPLES OF FEEDING FARM ANIMALS 
Uses of Feed.—It has been shown that the digested and assimi- 
lated feed is oxidized in the cells and tissues of the body; the 
chemical energy thus set free is utilized in one or more of three 
different ways: As kinetic energy, for the maintenance of the body 
heat,’or as mechanical energy, for the production of internal work 
in the body of the animal or for mechanical labor (horses, mules, 
and oxen), or as chemical energy stored in the form of animal 
products. If the energy supplied in the feed is more than sufficient 
to cover the demands for the first two purposes given, the excess 
may be stored up in the body in the form of animal products, like 
meat, fat, milk, eggs, etc., which may later serve to supply energy 
to man or other animals when used in their feed. 
The functions of the different components of feed are, briefly 
stated, as follows: 
Protein.—Flesh-forming substances. Essential for the produc- 
tion of lean meat, muscles, skin, ligaments, horns, hair, wool, milk, 
etc. When present in excess in the feed, used for production of body 
fat or as fuel, to give warmth and energy. Of general value in 
stimulating nutritive processes in the body. 
Fats.—Furnish fuel to keep the animal warm and produce 
energy. Aid in the production of fatty tissue. For the produc- 
tion of heat, 2.25 times as valuable as carbohydrates. 
Carbohydrates—Supply fuel to keep the animal warm and 
produce energy for muscular work. They are transformed into 
fats for the production of fatty. tissue.* 
Feed for Production.—The portion of the ration fed an animal 
over and above maintenance requirements is the productive part 
of the ration; the higher this can be increased up to the capacity 
of the animal for digestion and absorption of feed, the better are 
the returns obtained and the more economical is the production, 
so far as feed consumption is concerned. The amounts of nutrients 
required by the different farm animals for productive purposes have 
been determined in similar ways as in the case of the maintenance 
standards. The first attempts to formulate general standards for 
farm animals were made by the German scientist Grouven in 1858. 
He gave the quantities of total dry substance, protein, and fat 
which an animal of a certain age would require daily in its feed 
ration. A somewhat later effort in this direction is represented by 
the standards proposed by Wolff, in which the amounts of digestible 
components required by different classes of farm animals under 
varying conditions are given. 
*North Carolina Bulletin 106. 
