Digestibility How Determined 139 



Chester White pigs would digest rations differently from 

 Jerseys, Merinoes and Yorkshires. 



Young animals seem to digest high quality coarse 

 foods and grains as efficiently as older ones of the same 

 species, which is probably contrary to the popular belief. 

 There is doubtless a variation in the digestive power of 

 individual animals, but the data so far collected do not 

 show this with any degree of definiteness. In those in- 

 stances where the same four or more steers or sheep 

 have been used in determining the digestibility of sev- 

 eral feeding stuffs the highest coefficients were obtained 

 sometimes with one animal and sometimes with another. 



DETERMINATION OF DIGESTIBILITY 



If we accept as the undigested food the dry matter 

 of the solid excrement, which is practically .in accor- 

 dance with the fact, we have only to subtract this fecal 

 residue from the dry matter of the ingested food in order 

 to ascertain the amount and proportion digested. All 

 digestion experiments have proceeded on this basis.* 

 Animals have been fed at regular intervals a uniform 

 quantity of carefully analyzed food and the feces have 

 been collected, weighed and analyzed. From the data 

 thus obtained, the digestion coefficients have been cal- 

 culated. The method and the mathematics of such 

 experiments are so simple that correct results seem very 

 easy to obtain and they do possess an accuracy suffi- 

 ciently approximate to truth to render them useful in 

 practice. As digestion trials are usually conducted, the 

 coefficients of digestibility obtained for the dry matter 



* See note, p. 125. 



