COMPOSITION OF ANIMALS AND OF FEEDING STUFFS 69 



it by multiplication by 6.25 (or some other agreed factor) the 

 amount of protein is calculated. 



It is obvious that this method of determining protein is sub- 

 stantially a conventional method and that the adjective true 

 is employed in a somewhat Pickwickian sense. The result 

 probably includes all of the proteins of the feed but may also 

 include other insoluble nitrogenous compounds. 



106. Non-protein. The non-protein in feeding stuffs analy- 

 sis includes all the nitrogenous compounds which remain in 

 solution when the material is treated in the manner just de- 

 scribed for the determination of protein. The nitrogen may 

 be determined in the solution but ordinarily it is obtained by 

 subtracting the protein nitrogen from the total nitrogen. The 

 difference, multiplied by some conventional factor, equals the 

 non-protein. Obviously, the non-protein is a heterogeneous 

 mixture, varying as between different feeding stuffs and even 

 in the same feeding stuff grown or harvested under different 

 conditions. 



107. Nitrogen factors. Evidently the accuracy with which 

 the protein and the non-protein in a feeding stuff are determined 

 depends not only upon the accuracy with which the protein 

 and non-protein nitrogen can be separated and determined but 

 also on the correctness of the factors used for converting nitro- 

 gen into protein or non-protein respectively. 



For protein the usual factor has been 6.25 as already stated, 

 based upon the assumption of 16 per cent of nitrogen in average 

 protein. As was stated in Chapter I (44), however, different 

 proteins vary in their nitrogen content, and in particular the 

 vegetable proteins run higher in nitrogen than the animal pro- 

 teins, which is, of course, equivalent to a smaller conversion 

 factor. But while it is easily shown that the present factor is 

 incorrect in many cases, it is not so easy to find a substitute. 

 There is a rather wide range in the nitrogen content of the 

 individual vegetable proteins, while most feeding stuffs con- 

 tain two or more proteins in unknown proportions. Moreover, 

 the proteins of the majority of feeding stuffs, especially of the 

 roughages, have not yet been separated and studied. 



Ritthausen 1 has suggested the use of the factor 5.7 for the 

 majority of cereal grains and leguminous seeds, 5.5 for the oil 

 1 Landw. Vers. Stat., 47 (1896), 391. 



