THE DIGESTIBILITY OF FEEDINGSTUFFS 



59 



nutrient excreted in the feces, by multiplying the weight of 

 the feces by the per cent of each nutrient present in them, 

 and then dividing the result by 100. Thus the amount of 

 dry substance excreted in the feces was 12.6 times 36.48 

 divided by 100, or 4.6 pounds. The total amount of each 

 nutrient consumed, less the amount of that nutrient ex- 

 creted in the feces, gives the amount of each nutrient digested. 

 Thus in the example the hog digested 42.33 minus 4.60 or 

 37.73 pounds of dry substance. The amount of each nu- 

 trient digested, divided by the total amount of the cor- 

 responding nutrient consumed, and the result multiplied 

 by 100, gives the coefficient of digestibihty of each nutrient. 

 Thus the coefficient of digestibihty of the dry substance in 

 the above experiment was 37.73 times 100 divided by 42.33, 

 or 89.13 per cent. 



In the preceding example, the coefficients of digestibility 

 are calculated as follows : 



It should be noted, however, that coefficients of diges- 

 tibility are not exact because, as has already been shown on 

 page 47, the feces consist of dead and li\ang bacteria, dead 

 cells from the digestive tract, and the residues of the digestive 

 juices, as well as undigested food residues. However, such 



