Effects of Previous Nutrition, Feedlot Regimen and Protein Level on Feedlot Performance of Beef Cattle

Abstract

In Exp. 1, feedlot performance was measured using 200 mixed-breed heifers (276 kg and 231 d of age) previously subjected to different production systems (cornstalks vs cornstalks-grass). During the feedlot feeding phase, two energy regimens (corn vs corn silage-corn) and two protein (CP) levels (10.9 vs 12.8%) were provided. Heifers wintered on cornstalks (System 2) or wintered on cornstalks and summered on grass (System 3) had greater intakes (P < .05) and tended (P = .14) to gain faster (1.00 vs 1.21 kg/d) in the feedlot than heifers placed in the feedlot soon after weaning (System 1). Heifers managed under System 3 had greater intakes (P < .05) than heifers managed under System 2, although feed conversions (.122 vs .123 gain/feed) were similar for the two heifer groups. Feedlot regimen by protein level interactions were observed in Systems 2 and 3. Improved daily gains (P = .10) and feed conversions (P = .06) were found in heifers fed the high-CP diets (12.8%) when managed under the corn diet regimens but not in heifers managed under the corn silage-corn regimens. In Exp. 2, steers with compensating gain that were fed 11.4 or 12.4% CP finishing diets had faster (P < .05) gains and were more efficient in feed utilization (P < .05) than steers previously fed corn silage diets. Gains and efficiencies of compensating steers fed a 10.4% CP finishing diet did not differ from control steers fed 11.4% CP diets. Results of these studies suggest that cattle placed on high-energy finishing diets immediately after an extended period of nutritional restriction will respond to levels of protein higher than recommended; however, under more gradual realimentation regimens, additional protein is not warranted.