58 PRINCIPLES OF FEEDING FARM ANIMALS 



animal day and night. Other times, especially in case 

 of hogs, the animal is put into a stall or cage which has a 

 floor made of coarse wire screening through which the feces 

 drop on to a cloth stretched below. After collection, the feces 

 are weighed and analyzed. Knowing the total amount of 

 each nutrient which the animal consumes in a given time, and 

 the amount of each nutrient which it excretes in the feces 

 during the same time, it is an easy matter to calculate the 

 amount of each nutrient digested, and the coefficient of 

 digestibility of each nutrient of that particular feed. For 

 example, during a seven-day digestion period, a hog consumed 

 49 pounds of corn which had the follo^\^ng chemical composi- 

 tion : dry substance, 86.38 per cent ; crude protein, 9.80 

 per cent ; nitrogen-free extract, 70.03 per cent ; crude fiber, 

 1.91 per cent; and fat, 3.47 per cent. During this period, 

 the animal excreted 12.6 pounds of feces, which had the 

 following chemical composition : dry substance, 36.48 per 

 cent ; crude protein, 6.83 per cent ; nitrogen-free extract, 

 16.72 per cent ; crude fiber, 4.93 per cent ; and fat, 4.65 

 per cent. 



In order to find the coefficients of digestibility of the 

 nutrients of the corn in this experiment, one first obtains the 

 total amount of each nutrient consumed by the hog, by 

 multiplying the amount of corn consumed, — 49.0 pounds, 

 by the per cent of each nutrient in the corn, and then 

 dividing the result by 100. Thus the total dry substance 

 consumed was 49.0 times 86.38 divided by 100, or 42.33 

 pounds. The amounts of crude protein, nitrogen-free ex- 

 tract, crude fiber and fat consumed are ol)tained in similar 

 manner. 



The next step consists in determining the amount of each 



