92 



MAINTENANCE RATIONS OF FARM ANIMALS. 



In periods C and D of 1902 and period IV of 1903, the only ones in which 

 maintenance was reached, the crude protein ranged from 0.53 to 0.97 and the 

 true protein from 0.44 to 0.84. In a later series of experiments 1 on two 

 immature steers, from 0.92 to 1.13 pounds of crude protein, or 0.69 to 0.77 

 pound true protein per 1,000 pounds live weight sufficed for maintenance in 

 three periods in which there was some gain of fat. The experiments furnished 

 no evidence that so large an amount was necessary, since the next lowest 

 amount was 0.44 pound crude protein or 0.37 pound true protein in a ration 

 producing a slight gain of fat but a small loss of protein. 



The investigations of the Laboratory for Agricultural Research in Copen- 

 hagen upon the protein requirements for milk production include also two ex- 

 periments on dry cows 2 with rations furnishing relatively small amounts of 

 digestible nitrogenous matter, chiefly in the form of true protein. The periods 

 in which an approximate nitrogen balance was secured gave the following data : 



Nitrogen balance of dry cows per day and head — Copenhagen experiments. 



Cow and period. 



Live 

 weight. 



Crude protein 

 (N. X 6.25) digested. 



Gain of 

 nitrogen 

 per head 

 by animal. 



Per head. 



Per 1,000 

 pounds 

 live weight. 



Cow 117: 



Period 2 .- 



488 

 485 



466 

 443 



Grams. 

 87.5 

 100.0 



143.8 

 112.5 



Pound. 

 0. 18 

 .21 



.31 

 .25 



Grams. 



-3 

 +2 



-5 

 +3 



Period 4 



Cow 134: 



Period 1 



Period 4 





The experiments on milking cows also afford approximate data as to the main- 

 tenance requirement. If the protein of the milk is subtracted from the total 

 digestible protein of the feed, the remainder is obviously the maximum amount 

 which was available for maintenance. In Bulletin 139 of this bureau, 

 pages 38-39, there are given the results of those experiments in which the 

 smallest amounts of protein were consumed. Selecting from among these those 

 in which there was an approximate nitrogen equilibrium, we obtain the results 

 tabulated below : 



Daily gain or loss of protein by cows — Copenhagen experiments. 



Cow and period. 



Live 

 weight. 



Crude 

 protein 

 digested. 



Protein 

 of milk. 



Maximum 

 crude pro- 

 tein avail- 

 able for 

 mainten- 

 ance. 



Gain of 

 protein by 

 animal. 



Sixtieth report: 



Kilos. 



Grams. 



Grams. 



Grams. 



Grams. 



Cow No. 10, period 6 



446 



600.0 



387. 5 



212.5 



-12.5 



Cow No. 53, period 4 



454 



543.8 



350.0 



193.8 



-12.5 



Cow No. 53, period 6 



451 



568.8 



306.3 



262.5 



+18.8 



Cow No. 68, period 4 



461 



575.0 



393.8 



181.2 



-31.3 



Cow No. 68, period 14 



441 



506.3 



312.5 



193.8 



-12.5 



Cow No. 58, period 4 



485 



531.3 



325. 



206.3 



- 6.3 



Cow No. 58, period 6 



485 



581.3 



293.8 



287.5 



+37.5 



Sixty-third report: 













Cow No. 68, period 6 



453 



575.0 



368.7 



206.3 



-25.0 



1 Bureau of Animal Industry, Bulletin 128. 



2 Sixty-third Report, pp. 28 and 30. 



