44 PRINCIPLES OF FEEDING FARM ANIMALS 
ments from the body can be determined with great accuracy. The 
effect of a given ration on the nutritive processes in the animal 
body is thus ascertained, and it is possible to determine whether 
the animal lost or gained in flesh or body fat on the ration fed, 
and also the exact amount of the gain or loss. An example will 
illustrate how this information is obtained. 
A steer received daily the following amounts of nitrogen and 
carbon in the feed, water, and air: 0.44 pound nitrogen and 
13.25 pounds carbon; he excreted in the urine, dung, vapor, and 
gases given off during the 24 hours 0.35 pound nitrogen and 12.10 
pounds carbon, or there remained in the body 0.09 pound nitrogen 
and 1.15 pounds carbon. 
Pure muscular tissue (lean meat) contains, on the average, 16.67 
per cent nitrogen and 52.54 per cent carbon. The addition of 0.09 
pound nitrogen, therefore, equals 0.09 multiplied by 100/16.67, or 
0.54 pound of dry lean meat; this amount contains 0.28 pound car- 
bon (0.54 pound multiplied by 52.54/100). The difference between 
this amount of carbon and that remaining in the body is 0.87 pound. 
As only very small amounts of other non-nitrogenous components 
than fat are found in the body, we are safe in assuming that the 
excess of the carbon was used for the formation of body fat; as 
this contains, on the average, 67.5 per cent carbon, the difference 
of 0.87 pound equals 1.14 pounds of fatty tissue which. was added 
during the day. The steer gained 0.54 pound of dry lean meat and 
1.14 pounds body fat during the day. If the increase was 2.50 
pounds a day on the average throughout the experimental period, 
the difference, amounting to 0.82 pound, was composed of water 
and a small amount of mineral matter, both of which can be 
readily determined. 
Calorimetry.—The value of a feeding stuff for the nutrition of 
animals depends, to a large extent, on the amount of chemical 
energy that is set free when it is oxidized. This energy may be 
utilized for the production of body heat, work, or animal tissues. 
The burning of a material in a stove and the oxidation of the 
digested nutrients in the animal body are similar chemical proc- 
esses differing mainly in the intensity with which they run their 
course. In either case organic substances unite with the oxygen 
of the air or of the blood, respectively, and form carbon-dioxide and 
water (also urea in the case of protein substances oxidized in the 
body). The same amount of heat is given off whether the oxidation 
takes place in the body or outside of it. The heat evolved on com- 
bustion is a measure of the chemical energy which is stored up in 
