88 



MAINTENANCE RATIONS OF FARM ANIMALS. 



ing a maintenance ration, therefore, it is not sufficient to consider 

 simply the amount of protein, but account must be taken of the 

 supply of nonnitrogenous materials. 



VALUE OF NONPROTEIN. 



The crude protein of the feed of farm animals includes not only 

 true protein but a great variety of other nitrogenous substances, 

 grouped for convenience under the designation " Nonprotein." In 

 considering the results of experiments upon the protein require- 

 ments of these animals, therefore, it is necessary to determine 

 whether the true protein should be the basis of comparison or 

 whether the nonprotein has some value for maintaining the protein 

 tissues of the body. 



The writer has recently 1 considered in some detail the experimen- 

 tal evidence on this point, and the discussion need not be repeated 

 here. It appears to have been demonstrated by recent experimental 

 results, especially by those of Kellner, Morgen, and the Laboratory 

 for Agricultural Research in Copenhagen, that the nonprotein of 

 ordinary feeding stuffs is available for the maintenance of rumi- 

 nants, probably indirectly through a conversion to protein by means 

 of bacteria in the digestive tract. On the other hand, investigations 

 have not thus far shown that such nonprotein has any material value 

 for production purposes. The writer therefore reached the conclusion 

 th|it for the present, pending further investigation, it is desirable to 

 consider ordinarily only the digestible true protein in the compu- 

 tation of rations for productive purposes, ignoring the nonprotein. 

 This implies, however, that a discussion of the results of experi- 

 ments upon the protein requirement shall also be based upon the 

 amounts of true protein supplied and not upon the crude protein. 

 This will have two effects. 



First, it will make the protein requirement appear smaller than it 

 realh 7 is. Suppose, for example, that a series of trials in which the 

 ratio of digestible nonprotein to digestible protein is 1 : 10 shows 

 that nitrogen equilibrium is reached with a ration supplying 500 

 grams protein and 50 grams nonprotein. Regarding the true protein 

 only, the maintenance requirement is 500 grams, while the real re- 

 quirement of the animal is 550 grams. 



In the second place, however, this error will be largely compensated 

 for when the actual computation of rations is also based on the true 

 protein. Thus in the case just supposed, if a maintenance ration 

 be computed from any feed or mixture in which the ratio of non- 

 protein to protein is the same as in the experiments from which the 

 maintenance requirement was deduced, viz, 1 : 10, it is obvious that 

 the same final result will be reached whether the maintenance require- 



1 Bureau of Animal Industry, Bulletin 139. 



