DIGESTIBILITY OF STOCK FOODS 205 



Gains (i per cent of protein. So we are supplying the 

 oj i> poundi of protein pet day. U tin- manure from 

 the «»\ contain & per cent of protein, only one-half or 

 SO per cent of the proteifl of tin- haj tible. In 



iiu* wiiv we may determine the digestibility of the 

 other nutrients of the food. Such tests of food- as 

 these are (ailed DIGESTION EXPERIMENTS. 



In making digestion experiments much care and 

 patience ire required. For use in such tests only 

 healthy average animals should be selected, and for a 

 feu days before the beginning of the experiment the 

 animal must be fed nothing but the food to be tested. 

 In this time the manure resulting from any other food 

 eaten previously by the animal is passed from the body. 



Digestion experiments are usually continued for 

 several days or even week-, ind daring the time they 

 are in progress the animal must be carefully looked 

 ■Iter. Samples of the food to be tested must be care- 

 fully analysed to determine the amounts of its 

 nutrients; and at certain intervals the animal must be 

 supplied with weighed quantities of the food. All the 

 manure, both liquid and solid, passed by the animal 

 during the experiment should be collected and weighed. 

 Samples of the manure are analyzed in order to deter- 

 mine the amounts of the nutrients left in it; a number 

 of samples being taken, each at a different >tage of the 

 experiment. The average amounts of the nutrients in 

 the manure arc subtracted from the average amounts 

 of the saUM nutrients in the .food, and the results show 

 the imounti of digested nutrients. With figures 

 determined in this way we may easily calculate the 



