DIGESTION 



409 



is possible that the fermentation and other changes which food 

 undergoes within the animal, modify the crude fiber so that a 

 portion of it becomes soluble in acids or alkali, and thus appears 

 as a portion of the nitrogen-free extract. 



Digestibility of Ether Extract Constituents. The ether extract 

 of concentrates consists chiefly of fats and oils, but that of rough- 

 ages contain on an average nearly 60 per cent, unsaponifiable mat- 

 ter, chiefly wax alcohols, as previously pointed out. It has been 

 long observed that the ether extracts of hays and fodders have 

 a low digestibility. Indeed, in a number of experiments, more 

 ether extract was found in the excrement than was present in the 

 hay. 



A study of the digestibility of the constituents of the ether 

 extract shows that while the unsaponifiable materials or wax 

 alcohols have a low coefficient of digestibility, the saponifiable 

 material, containing the fatty acids and chlorophyll, have a much 

 higher digestibility. Thus the observed low digestibility of the 

 ether extract of hays and fodders is due to the small content of 

 fats and oils and the high content of waxes and alcohols less 

 easily digested. 



PERCENTAGE DIGESTIBILITY OF CONSTITUENTS OF ETHER EXTRACT^ 



Composition and Heat Value of Digested Nutrients. We may 

 determine the composition of digested crude fiber by the follow- 

 ing method : The crude fiber fed in the feed and the crude fiber 

 excreted in the digestion experiment are subjected to analysis. 

 The quantity of carbon, hydrogen, and oxygen fed in the crude 

 1 Fraps and Rather, Bulletin 150, Texas Station. 

 27 



