274 MANUAL OF CATTLE-FEEDING. 



If a concentrated fodder decreases tlie digestibility of 

 the coarse fodder with which it is fed, we should expect 

 that watli a greater relative quantity of the former in the 

 ration the decrease in the digestibility of the ration as a 

 whole would be also greater. 



We therefore proceed as follows : in a first period we 

 determine the digestibility of the coarse fodder — hay, for 

 example — ^w^hen fed alone. In a second period we add to 

 the hay a certain amount of the concentrated fodder in 

 question — maize meal, for instance — and determine the 

 digestibility of the mixture. In a third period we increase 

 the relative quantity of me^l very considerably, and deter- 

 mine the digestibility of this mixture. 



Now, assuming the digestibility of the hay to have been 

 the same in the second and third periods as in the first, we 

 calculate, from our experimental results, the digestion co- 

 efficients for the maize meal in the second and third 

 periods. 



It is obvious that, if neither feeding-stuff has altered the 

 digestibility of the other, these two sets of digestion co- 

 efficients ought to be the same within the limits of experi- 

 mental eiTOi*, and, in that case, we have not only proved' 

 this fact but have also determined the digestibility of the 

 mai^e meal. 



On the other hand, if the digestibility of either feeding- 

 stuff has been diminished by the presence of the other, it 

 is plain that our method of calculating the results will 

 show an apparent decrease in the digestibility of the 

 maize laeaL In the case supposed it would be impossible 

 to determine directly in which of the two feeding-stuffs 

 the decrease took place, and the method of expressing the 

 results would depend partly on the results of other experi- 

 ments and partly on questions of convenience. 



