FEEDING UREA TO DAIRY COWS^ 

 By J. G. Archibald, Research Professor of Animal Husbandry 



INTRODUCTION 



The idea of using urea and othier relatively simple nitrogenous compounds as 

 substitutes for protein in the rations of farm animals is not a new one. Investi- 

 gations bearing on the problem date back to the middle of the 19th century. In 

 1891 Zuntz (1) suggested that ruminants may obtain protein from nonprotein 

 nitrogen through synthesis by the bacteria and other microorganisms normally 

 found in the rumen or first stomach of this class of animals. The scarcity of 

 nitrogenous concentrates in Germany during World War I and the development 

 of processes for fixation of atmospheric nitrogen gave a great impetus to investi- 

 gations suggested by the earlier work. Most of the work on the problem during 

 and closely following the war was done in Germany. Numerous investigators 

 there claimed to have shown that such compounds as urea, ammonium carbonate, 

 and ammonium acetate could be utilized by the flora of the rumen for building 

 up cellular proteins, which in turn could be digested in the abomasum or true 

 stomach of the ruminant in the same manner as the preformed proteins of the 

 ration. 



More recent critical reviews have questioned the validity of these findings. 

 Mitchell and Hamilton (2) in 1929 concluded "that the bacterial-protein theory 

 of the utilization of non-protein substances by ruminants is still in the contro- 

 versial stage." Krebs (3) in 1937 reviewed the whole subject and stated that the 

 evidence was all based on feeding trials of insufKcient length— that long-time 

 trials are necessary in order to establish the theory on a sound basis. Marston 

 (4) in 1939 wrote that "the hypothesis that protein in useful amounts is syn- 

 thesized through the agency of the micro-flora of the rumwi is, on the whole, far 

 from convincing." 



Along about 1930, manufacture of synthetic urea on a commercial basis became 

 a reality in the United States. It was used at first largely for fertilizer, but as 

 production expanded the manufacturers began to look for other outlets. The 

 above-mentioned work suggested a possible market in the feed trade, but several 

 investigators and E. I. DuPont de Nemours and Co., principal producers of urea 

 in this country, felt that, in view of the unsettled status of the problem, further 

 research should be conducted by American experiment stations. Urea feeding 

 experiments, therefore, were initiated by several institutions including Hawaii, 

 Illinois, Kansas, Massachusetts, New York (Cornell), and Wisconsin. The 

 investigations have included experiments with beef cattle, dairy cattle, and sheep. 

 At least four of these institutions are still investigating various phases of urea 

 feeding; because of circumstances beyond its control, the Massachusetts station 

 has been obliged to discontinue its urea feeding project for the duration of the 

 war at least. This bulletin constitutes a report of the work done here from 

 January, 1940, through December, 1942. 



'Acknowledgement is made (1) of financial assistance from E. I. DuPont de Nemours and 

 Company, Wilmington, Delaware, which made possible the conduct of this investigation: and (2^ 

 of the cooperation of the State Department of Mental Health, which made available facilities for 

 the feeding trials at one of the State institutions under its control. Especial thanks are due to 

 Mr. Rodman C. Nowers, Head Farmer at the Medfield State Hospital, who had immediate super- 

 vision of the feeding trials, and whose careful attention to the details of the work contributed in 

 arge measure to its success. 



