684 NUTRITION OF FARM ANIMALS 



the percentage efficiency of the protein. If this be done, using 

 the approximate data contained in Chapter IX (415-417), the 

 percentages of the proteins supplied in excess of maintenance 

 which were retained would be distinctly increased in every case. 

 It cannot be concluded, therefore, that the low percentages 

 computed by the Wisconsin investigators show that only these 

 rather small proportions of the cereal proteins are capable of 

 transformation into body proteins. On the other hand, how- 

 ever, such a conjectural correction would result in making the 

 relative differences between the different proteins appear 

 greater than those shown by the method of calculation used. 



No other studies upon the relative values of the mixed pro- 

 teins of feeding stuffs have come to the writer's notice. 



Value of non-protein 



In a previous paragraph (782) the conclusion was reached 

 that for the present the only available measure of the protein 

 values of feeding stuffs is the total amount of digestible pro- 

 tein which they contain. In the application of this method 

 it; becomes necessary to decide whether the basis of compari- 

 son shall be the " crude " protein or the " true " protein as de- 

 termined by existing conventional methods (104-107) ; in other 

 words, to decide what value, if any, shall be assigned to the 

 non-protein. 



786. Early investigations. Following the recognition of 

 the fact that the substances grouped under the collective term 

 non-protein make up a considerable share of the nitrogenous 

 matter of numerous feeding stuffs, much labor has been ex- 

 pended in efforts to determine their nutritive value as com- 

 pared with that of the true proteins. These investigations 

 have been summarized by the writer elsewhere. 1 While 

 much diversity of opinion has prevailed, the general tendency 

 has been to consider the non-protein as of questionable value. 

 Kellner, the leading German authority, in particular, regarded 

 it as valueless. 



787. New viewpoint. With advancing knowledge of the 

 chemistry of the proteins and of the chemical mechanism of 



1 Principles of Animal Nutrition, pp. 52-58 ; U. S. Dept. Agr., Bur. Anim. Indus., 

 Bui. 139 (1911). 



