THE DIGESTIBILITY OF FEEDINGSTUFFS 



63 



all the errors of the determination are thrown upon one feed. 

 Consequently absurd results are often obtained, as in the 

 case of the coefficient of digestibility of fat in the previous 

 example. Thus at the Illinois Station/ Grindley, Carmi- 

 chael, and NewHn fed four pigs a ration of middings alone ; 

 later a ration of com and middlings in equal parts ; and then 

 a ration of corn alone. The coefficients of digestibihty of 

 corn and middUngs as actually determined were materially 

 different from the coefficients calculated indirectly by the 

 method just described. Thus the average coefficients of 

 middhngs when determined directly and when determined 

 indirectly when fed with corn, were as follows : 



This shows that the indirect method is not exact by any 

 means. However, this is the only method of determining 

 the coefficients of digestibility for each feed when more than 

 one feed is used and, until a better one is formulated, it 

 must be used. 



Knowing the coefficients of digestibility of two feeds, a 

 third may be added to the ration, and its digestibihty cal- 

 culated in a similar manner. 



Digestibility of Mineral Matter. — Owing to the many 

 errors involved in the determination, and the great variability 

 of the results obtained, the coefficients of digestibility of min- 



^ Unpublished data. 



