RELATIVE VALUES OF FEEDING STUFFS 6oi 



various authors, including many of the agricultural experiment 

 stations, and it is an easy matter for the feeder to learn what 

 amounts and kinds of digestible nutrients any given feed or 

 ration will supply. 



In view of the extensive use of such tables it is important 

 that the exact significance of the results which they embody 

 should be understood. As a mere matter of logical concep- 

 tion, the comparison of feeding stuffs on the basis of their 

 digestible nutrients is inferior to that based on hay values or 

 on feed units. In these methods the attempt is made, how- 

 ever crudely, to compare the actual effects produced by the 

 feeding stuffs in the animal body. A determination of diges- 

 tibility, on the contrary, affords no direct information whatever 

 as to the nutritive effect of the materials digested. It is not 

 even necessary to weigh the animal in a digestion trial. The 

 comparison of feeding stuffs on this basis is between what they 

 contain and not between what they accomplish. 



Nevertheless, tables of digestible nutrients have been of great 

 value in promoting more rational and profitable feeding, but it 

 is becoming increasingly evident that they express but part of 

 the truth. The essential feature of the newer methods of 

 comparison outlined in this volume is not that they employ 

 units of energy as a basis of comparison but that they con- 

 stitute a return to the logical conceptions which were at the 

 basis of the early methods and which were discussed in so il- 

 luminating a manner by Henneberg and Stohmann in the 

 introduction 1 to their " Neue Beitrage " in 1870. These 

 newer methods seek to determine, by more elaborate and 

 accurate methods than were available to the earlier experiment- 

 ers, the actual effect of the feed on the body of the animal as 

 well as its content of matter and energy. 



3. CONDITIONS AFFECTING DIGESTIBILITY 



711. Digestibility variable. Not only is the current method 

 of estimating the relative values of feeding stuffs, as described in 

 the previous section, based largely on the digestibility of the ma- 

 terials in question, but the latter is also a most important fac- 



1 Uber das Ziel und die Methode der auf den landwirtschaftlichen Versuchs- 

 stationen auszufuhrenden thier-physiologischen Untersuchungen. 



