Digestion, Bespiration and Calorimetry. 29 



ucts to the excreta as well as gtmnny substances originating from 

 tissue changes of the alimentary tract. 



The digestibility of protein in coarse fodders varies widely, 

 ranging from 35 to 80 per cent. Usually the higher the ratio of 

 protein to non-nitrogenous constituents in a feed the greater the 

 percentage of the protein digested. 



Of the crude fiber from 30 to 70 per cent, is digestible by 

 ruminants, while for the pig and the horse it is considerably less. 

 The larger utilization of cellulose by ruminants is probably due 

 to the fact that the food undergoes more thorough preparation for 

 digestion in the primary stomachs. The addition to the ration 

 of a food rich in protein aids the digestion of cellulose. 



The sum of the digestible nitrogen-free extract and the digest- 

 ible crude fiber about equals the total nitrogen-free extract of any 

 given feed. 



The digestibility of ether extract varies greatly in different 

 feeding stuffs, ranging from 30 per cent, in straw to over 90 in 

 the cereals. The digestibility of the several compounds grouped 

 under this term cannot be as accurately determined as in case of 

 the other nutrients, owing to a variety of substances appearing 

 in the solid excrement, which, although dissolved from it by 

 ether, cannot be considered as nutritive material that has escaped 

 iigestion. The small quantity of the ether extract usually 

 present in feeding stuffs also renders the deterndnation of this 

 component more liable to error. 



Zuntz and Lehmann report that the work of chewing the food 

 and digesting it, in the case of the horse, may represent a consid- 

 erable proportion of the nutritive value of the food. The effort 

 in chewing hay represents 11.2 per cent., and in oats 2.8 per 

 cent, of the total energy yielded by the food. 



50. digestion of coarse fodders. — The leading points of Wolff's 

 lucid statements on this subject i are here presented, the first ones 

 having reference to coarse fodders fed without the addition of 

 grain. 



The quantity of fodder supplied the animal does not affect the 

 digestibility of the several constituents. Healthy animals under 



1 Fai-m Foods, English edition. 



