FEEDING UREA TO DAIRY COWS 15 



and milk production the urea was not on a par with the standard protein con- 

 centrates contained in the regular ration. It seems appropriate to briefly re- 

 capitulate these differences. 



The cows on the regular ration maintained their general condition somewhat 

 better than those fed the urea ration; the trend in milk production and milk 

 shrinkage favored the regular ration in both the "double reversal" and the 

 "continuous" groups; and a group of cows that had been kept on the urea ration 

 continuously for two years shrunk more rapidly in milk flow when placed on a 

 control ration than a similar group that had been on the regular ration for the 

 same period of time. The cumulative effect became more evident as the trial 

 progressed, and illustrates rather clearly the inherent fallacy of drawing conclu- 

 sions from short-time trials in this type of work. 



It is recognized that the results of these trials are in some respects at variance 

 with results obtained elsewhere in this country. Workers at the Wisconsin 

 station have obtained results which indicate that urea can be satisfactorily sub- 

 stituted for linseed meal in the grain mixture for milking cows. On the whole, 

 however, their results are not substantially different from those here reported 

 and what differences there are may be due in part to the fact that these cows 

 were on the average somewhat heavier producers, their average annual milk 

 yield in the lactation immediately preceding the trial being in excess of 13,000 

 pounds. 



Everything considered, it seems probable that urea will find a place in the feed 

 trade as a partial protein substitute in grain mixtures for ruminants. It should 

 be introduced with caution and its limitations duly recognized. The maximum 

 amount fed should be not more than 3 percent of the grain mixture; it should be 

 fed only to ruminants, i. e., to animals such as cows which have a multiple stom- 

 ach; and it should be fed in conjunction with feeds which furnish liberal amounts 

 ol starch or other readily soluble carbohydrates. The reasons for these restric- 

 tions are twofold: first, the bacteria and other microorganisms which form protein 

 from urea function on a worthwhile scale only in the paunch or first stomach of 

 ruminants, and second, these organisms requ-'re a supply of readily fermentable 

 carbohydrate in order to grow and multiply efficiently. Within these limits and 

 assuming that a worthwhile tonnage can be released from its preseat use for 

 explosives antl fertilizer, urea can be of considerable aid in helping to relieve the 

 present serious shortage of nitrogenous concentrates. 



SUMMARY 



Twenty-eight Holstein cows were used in a three-year trial to determine the 

 adequacy of urea as a partial substitute for protein in milk production. The 

 maximum amount of urea fed was 3 percent of the grain mixture; it supplied 

 approximately 42 percent of the total nitrogen in the grain and 25 percent of 

 the total nitrogen in the entire ration. It was compared with such standard 

 protein concentrates as cottonseed meal, soybean oil meal, and corn gluten feed, 

 by two systems of feeding trials, double reversal and continuous. A control 

 ration containing no urea was fed to some of the cows as a check on the adequacy 

 of the basal ration. 



Results showed that considerable use was made of the urea, although it was 

 not quite on a par for maintenance and milk production with the standard protein 

 concentrates. With due recognition of its limitations, urea will undoubtedly 

 find a place in the feed trade, especially in times of protein shortage such as we 

 are now experiencing. 



