THE PRODUCTION VALUES OF FEEDING STUFFS 687 



off in production. For maintenance alone, non-protein seemed 

 quite effective, but neither for growth nor for milk production 

 could it equal protein. It seems probable that the limiting 

 factor in this indirect utilization of non-protein is the extent to 

 which it can be synthesized into protein by the microorganisms 

 rather than any inferiority in the nutritive value of the result- 

 ing protein. 



789. Conclusions. It seems clear that the evidence is in- 

 sufficient to warrant any general conclusions regarding the nu- 

 tritive value of non-protein, if indeed any general statement 

 regarding such a heterogeneous group is possible. Ultimately, 

 it may be that studies of the amino acid yields of the total ni- 

 trogenous matter (crude protein) of feeding stuffs, or com- 

 parisons of its relative efficiency in supporting maintenance or 

 growth, will lead to the formulation of production values for 

 the crude proteins of different materials, but for the present 

 the writer feels that the safer course is to make the digestible 

 " true " protein, so-called, the basis of comparison. 



While some experiments, notably the Copenhagen experi- 

 ments on dairy cows (586), seem to indicate a relatively high 

 value for the non-protein of roots especially, most investigators, 

 particularly Morgen and his associates, have, as already noted, 

 found them decidedly inferior to protein. It is true that the 

 non-protein contains amino acids which may at times be utilized 

 indirectly by herbivora through the agency of the microor- 

 ganisms of the digestive tract, but even this indirect utilization 

 seems to be rather limited in extent in most instances. The 

 conventional " true " protein, on the other hand, may be re- 

 garded as representing approximately the real proteins of a 

 feeding stuff and it would seem that these mixed proteins are 

 likely to supply more nearly a balanced amino acid mixture in 

 digestion than would result from the inclusion of the non-pro- 

 tein. Investigations of the protein values of feeding stuffs 

 should doubtless take account of whatever amino acids the 

 non-protein supplies, i.e., they should relate to the crude pro- 

 tein. With continued study of these relations, it may be hoped 

 that greater clarity may be attained, but until that end is 

 reached, the digestible " true " protein seems the safer basis 

 for the formation of tables of the production values of feeding 

 stuffs and for the computation of rations. Whatever error is 



