874 



EXPERIMENT STATION RECORD. 



r Vol. 43 



Utilization of increased supply of nitrogen by dairy coios for body and milk pro- 

 teins in relation to concentrates fed and energy supplied by roughage. 



' In the case of cow 3 of the 1918 series the gluten feed period preceded the linseed mesl period. 



The coinimtuti(His by the niodirted Thomas method gave re.sult.s very closely 

 resembling those in the table, on the average 52.4 per cent of the linseed meal 

 nitrogen and 76.4 per cent of the gluten feed nitrogen being utilized to establish 

 nitrogen equilibrium. 



The fluctuations in the degree of utilization of nitrogen are thought to be due 

 in great part to fluctuations in the energy intake. " When the percentage of 

 therms furnished by the hay and silage was low the protein in the gluten feed 

 or oil meal was used principally as a source of energy and could not be used to 

 build up the body tissue or to furnish milk protein. Therefore the percentage 

 availability of* the feed nitrogen was extremely low in these cases." The 

 Armsby standards were used in estimating the energy requirements. The 

 sequence of feeds also seemed to influence the utilization. Although in the last 

 period of series 2 no concentrates were fed, all the 4 nitrogen balances were 

 positive. 



Cow 4 of the 1918 series was aberrant in that more nitrogen was digested in 

 period 1 than in periods 2 and 3. However, the negative nitrogen balance during 

 the first period was slight, and consequently only small amounts of concentrates 

 were fed the following periods. 



Proximate analyses of the feeds offered in each period are tabulated, and 

 besides the nitrogen data the records include the intake and outgo of fats, 

 fiber, nitrogen-free extract, and ash. 



The effects of high protein and high energy rations in feeding dairy 

 cows [I (continued) ], W. B. Ellett and C. W. Holdaway {Virginia Sta. 

 Tech. Bui. 20 {1920), pp. S-16). — The authors report the results of a 10-day 

 digestion and nitrogen-balance experiment conducted in June, 1917, with two 

 Holstein cows that had been kept continuously on a high energy and a high 

 protein ration, respectively, since September, 1915. The amounts of feed 

 offered (11 lbs. of grain and a maximum of 40 lbs. of silage per day) were 

 the same in both cases, but the grain mixture for the cow on the high energy 

 (low protein) ration consisted of corn meal and bran (9:2), while the high 

 protein grain mixture consisted of gluten meal, bran, and cottonseed meal 

 (7:2:2). During the trial the low protein ration provided 9.9 therms of energy 

 (using actual digestion coefficients), while the cow required on the Armsby 

 standard only 7.43 therms. The protein-rich ration provided 13.06 therms, 

 which was also higher than the cow's requirement of 11.56. The former cow 

 gave 1.84 kg. of milk per day and the latter 6.8 kg. A similar experiment with 

 the other two cows in this project was reported in Technical Bulletin 12 



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