Purdue University Agricultural Experiment Station Lafayette, Indiana
Mimeo A.S. 246 April 24, 1959
THE EFFECT OF REPLACING SOYBEAN MEAL WITH UREA AND CORN IN THE RATIONS OF FATTENING CATTLE IN DRYLOT AND ON PASTURE
W. M. Beeson and T. W. Perry
Department of Animal Science
Urea has been used as a protein extender or replacer in the rations of beef cattle and sheep for a number of years# However, the actual safe and practical maximum level of protein that can be replaced with urea has not been definitely established. As a result, the recommendations for feeding urea usually make an allowance for a margin of safety# Thus, a replacement of not more than one-third of the natural protein with urea has been accepted as a standard under usual feeding conditions#
The objective of the trials reported in this mimeograph was to determine the effect of replacing from 0 to 100$ of the soybean meal protein with urea and corn in the fattening rations of beef cattle under either drylot or pasture conditions.
Experimental Procedure
Trial I.
Sixty Hereford steers, 2 years of age and averaging 923 pounds, were divided into four drylots of 15 each to be hand fed a fattening ration of a full feed of ground shelled corn, 3*5 pounds of Purdue Supplement A, plus ground corn cobs and minerals. Cne lot served as the control and received the ration indicated. The other three lots were fed urea modifications such that a combination of urea and corn replaced the soybean meal contained in Supplement A by 1/3, 2/3 and 3/3, respectively, on a pound for pound and nitrogen replacement basis (Table I lists the composition of the supplements fed). At the completion of the 133”day fattening trial, each of the four lots was shipped to Chicago, Illinois, and sold by separate lots. Carcass data were obtained at the time of slaughter.
Trial II.
Eighty yearling Hereford steers averaging 672 pounds were divided into four pasture lots of 20 each and were self fed a complete mixed fattening ration, free choice, composed of 9 parts ground ear corn to 1 part of Supplement A, plus minerals and pasture. As listed for Trial I, above, one lot served as the control and received the ration listed. In the rations of the other 3 lots, urea and corn replaced the supplemental soybean meal at levels of 1/3, 2/3, and 3/3, respectively.
At the conclusion of the pasture season (140 days), the four lots of cattle were moved to drylot and were fed the same except that the free choice complete mixed ration was changed from 9 parts ground ear corn to 1 part supplement, to a ratio of 8 to 1 for the next 74 days. In addition, a small amount of mixed hay was available. At the conclusion of the experiment, the cattle were marketed at Indianapolis, Indiana, where marketing and carcass data were obtained.
Results
Trial I. (Drylot)
During the first two weeks of the trial, cattle receiving a part of their protein equivalent as urea (Lots II, III and IV), apparently went through a period of adjustment in their digestive system. During this two-week period of apparent