Effect of Protein Withdrawal on the Performance of Steer Calves

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Abstract
Two feedlot trials were conducted with 72 and 96 Hereford steer calves to evaluate the effect of feeding supplemental protein for different lengths of time during the finishing period. Also evaluated in the first trial was the feeding value of three types of corn grain. In the first study, there was no difference in the performance of steers fed either normal, opaque-2 or waxy corn grain. Steers fed no supplemental protein (7.48% dry basis) during the first 70 days on trial gained less (.34 kg) (P<.01) than steers fed supplemental protein (10.82%) (1.30 kg). When supplemental protein was withdrawn from steers at 70 days (weight 368 kg), daily gain (.17 kg) was less than steers fed supplemental protein (1.03 kg) for the next 84 days, and feed conversions increased from 6.67 to 28.69 kg dry feed per kilogram of gain. When steers weighed 430 kg, the removal of supplemental protein at 140 days reduced daily gains from 1.04 to .43 kg and increased feed conversions from 7.69 to 14.90. Overall, cattle withdrawn from protein gained less (P<.01) than cattle fed supplemental protein. In the second experiment, steers fed no supplemental protein initially (8.66% dry basis) (weight 334 kg) gained less (P<.05) the first three consecutive 28-day weigh periods and required more (P<.05) dry feed per kilogram of gain the first two weigh periods than did those steers fed supplemental protein (12.82% dry basis). Steers withdrawn from supplemental protein at 56 days (weight 397 kg) gained less (P<.05) and required 20% more dry feed per kilogram of gain the first 28-day weigh period after supplemental protein withdrawal than steers fed supplemental protein. Feeding no supplemental protein the final 88 days of this experiment had no effect (P>.10) on steer performance when analyzed by individual weigh periods. The feeding of no supplemental protein for the entire experiment reduced daily gains from .95 to .75 kg and increased feed conversions from 7.26 to 8.78. When supplemental protein was withdrawn from the ration at 56 days, daily gains were less (.77 vs .89 kg) and dry feed required per kilogram of gain increased from 8.37 to 9.38 for steers fed no supplemental protein the next 116 days. The withdrawal of supplemental protein at 112 days (weight 409 kg) depressed daily gain but had no effect on the feed conversion of steers the final 60 days of the experiment. Steers receiving a "Dehy"-vitamin-mineral supplement after protein withdrawal gained more (.90 vs .79 kg) (P<.05) and were more efficient (P<.05) than steers fed a corn-vitamin-mineral supplement after supplemental protein withdrawal. Steers fed no supplemental protein for the entire experiment had lower (P<.05) dressing percentages but improved yield grades when compared to cattle fed supplemental protein for 56, 112 and 172 days. The primary effect of the withdrawal of supplemental protein in the ration of growing-finishing steer calves in both experiments was to depress the daily dry matter intake. Copyright © 1976. American Society of Animal Science . Copyright 1976 by American Society of Animal Science