492 NUTRITION OF FARM ANIMALS 



of dairy cows carried on at the Laboratory for Agricultural 

 Research in Copenhagen 1 and unpublished respiration experi- 

 ments by Kellner. 2 The experiments of Hart and Humphrey 

 mentioned in the next paragraph, when computed in the same 

 way, also show a high percentage utilization of the digested 

 protein, although the gains and losses of body protein are 

 relatively so considerable as to disturb the comparison. 

 Haecker's low protein rations in 1902-3-4-5, as noted on a 

 subsequent page (602), seem to afford another example of the 

 high utilization of feed protein. 



While too much weight should not be attached to the results 

 of comparisons like the foregoing, especially since they include 

 a more or less uncertain estimate of the protein requirement 

 for maintenance, they nevertheless seem to indicate beyond 

 reasonable doubt that on low protein rations the protein of at 

 least some feeding stuffs may be converted into milk protein 

 without any very large loss. 



587. Relative values of proteins for milk production. The 

 considerations advanced in preceding chapters (400, 465) regard- 

 ing the relative values of different proteins for maintenance and 

 for production render it altogether probable that they also differ 

 in value as sources of milk protein. No experiments on this 

 point have as yet been reported, but Hart and Humphrey 3 in 

 two series of experiments on cows have compared the mixed 

 proteins of maize, wheat, gluten feed, oil meal and distillers' 

 grains with proteins prepared from milk (784), using maize 

 stover and silage as roughage. They found the average per- 

 centage of the resorbed nitrogen which was recovered in the 

 milk yield plus the gain (or minus the loss) of the body protein 

 to be 



Skim milk powder 59 % 



Casein 59% 



Maize 40% 



Wheat 36% 



Gluten feed 45 % 



Oil meal 61 % 



Distillers' grains 60% 



1 Denmark-Beretning fra den Kgl. Veterinea-r of Landbohojskoles Laboratorium 

 for landokonomiske Forsog. 6ode, 1906, and 63de, 1907, Kobenhavn. Translated 

 by Mallevre, Societe de 1'Alimentation Rationale du Betail. Compte Rendu de 

 ueme et i2eme Congres. 



2 Die Ernahrung der landw. Nutztiere, 6th Ed., 1912, p. 551. 



3 Jour. Biol. Chem., 21 (1915), 239; 26 (1916), 457. 



