io6 THE CHEMISTRY OF CATTLE FEEDING 



produces an apparent reduction in the digestibility both of the 

 nitrogenous and non-nitrogenous nutrients. At all events, 

 larger amounts of both are found in the faeces. It is probable, 

 however, that the increased amount of nitrogenous matter 

 found in the faeces is not derived from the food but from the 

 digestive juices which are secreted in larger quantities under 

 these circumstances and possibly, in part, from the mucous 

 lining of the intestines. The diminution of the digestibility 

 of the non-nitrogenous matter is real. It has been suggested 

 that bacteria, which play an important part in the process, are 

 able to obtain a sufficiency of nourishment in the more readily 

 digestible substances which have been added and do not, 

 therefore, act so strongly upon the coarser fodder. This 

 hypothesis is open to very serious objections; but whatever 

 the true explanation may be there can be no doubt as to the 

 fact. 



The addition of considerable quantities of carbohydrates 

 does not affect the digestibility of foods that are relatively rich 

 in nitrogenous matter. It is only when the amount of carbo- 

 hydrates is excessive, i.e. more than about ten of the latter to 

 one of nitrogenous matter, that this effect is produced. The 

 tendency of large quantities of carbohydrates to reduce the 

 digestibility of other foods can be corrected by adding more 

 nitrogenous matter till the balance is restored ; and it is found 

 that amides are as effective as true protein in this respect. 



Excessive quantities of fat are not easily digested by the 

 herbivora, and the addition of such to other food tends also to 

 reduce the digestibility of all the constituents by protecting 

 them from the action of the aqueous digestive juices. The 

 addition of small quantities of fat to foods that are naturally 

 poor in that ingredient has no perceptible effect on the 

 digestibility, provided the fat is thoroughly broken up by mixing 

 with the other foods. It is considered inadvisable that the 

 amount of fat should be more than about 10 per cent, of the 

 nutrients. 



The coefficients of digestibility for any food depend, to 

 some extent, upon the digestive capacity of the animals 

 experimented on. The most striking differences are those 



