230 



Agricultural Chemistry. 



quantities of the feed, the composition of which has been de- 

 termined by chemical analysis. During the experiment the solid 

 excrement is collected and weighed and finally analyzed by the 

 same methods as those previously applied to the feed. From the 

 data thus collected the digestion co-efficients are calculated. 

 Example : 



Digestion Experiment with Sheep (From Henry). 



From the example it will be seen that the digestion co-efficient 

 is the proportion of each food constituent digested out of 100 

 parts by weight supplied. The figures secured are not absolutely 

 accurate, due to intestinal secretions which become reckoned as 

 undigested food. The co-efficients for proteins and fats suffer 

 most in this regard. In experiments with oat straw the fecal nit- 

 rogen has been found to be more than that in the food, although 

 the protein of the straw must have been digested to a considerable 

 extent. Jordan states: "It is probably safe to affirm that at 

 least 10 should be added to the co-efficients of digestibility of the 

 protein of coarse fodders, as usually given in the tables that have 

 been compiled." With fat co-efficients, an error is introduced 

 through the secretion of bile into the intestine. This material 

 contains products soluble in ether, the usual reagent used in de- 

 termining the fat content of the feeding stuff. Consequently the 

 undigested fat appears larger than it really is. 



