DIGESTION OF THE FOOD 29 



These last figures are termed the " Coefficients 

 of Digestibility." 



If the digestibility of the protein is to be calcu- 

 lated, then the non-protein substances (in this case 

 I, 35% ==0 ' 99 kilos) have to be deducted from 

 the crude protein in the food and from that in the 

 dung. This would be in the above experiment 

 0-684 ~ 0-099 = °'5&5 kilos for the protein in the 

 food, and 0-342-0-099 = 0-243 kilos digested, which 

 equals 41-5% digestible protein. 



From what has been said it will be seen that the 

 assumption is made that the dung consists only of 

 undigested food. This assumption, however, is 

 not quite correct, for the faeces are always mixed 

 with small quantities of substances which come 

 from the digestive organs and which are termed 

 the products of metabolism. At present there are 

 no methods by which these can be separated from 

 the dung, so the supposition has to be made that 

 all which is found in the dung is undigested 

 food. 



If digestion experiments have to be made with 

 easily digested foods such as roots, cereal grain 

 meals, oil cakes, etc., which cannot be fed alone to 

 ruminants or horses, then some coarse fodder — 

 hay or straw — the digestibility of which has pre- 

 viously been determined, must be given at the same 

 time. 



From these two experiments all the data neces- 



