Effect of phase-feeding crude protein on performance and carcass characteristics of crossbred beef bulls: an application to reduce nitrogen compounds in beef cattle diets

Beef cattle (24) with an average initial body weight of 417 ± 54 kg were assigned in a 2 × 2 factorial design with six repetitions. The factors studied were two levels of CP: 11 (low CP) or 13 % (high CP) in the initial feedlot phase (days 1 - 36) and in the final phase (days 37 - 72). After 36 days, half of the bulls fed with each level of CP were selected to reverse the CP level. No interaction was observed (P > 0.05) between the level of protein in the initial and final phases on the intake of the nutrients evaluated. There was no effect (P > 0.05) of the protein levels in the initial and final phases on intake of dry matter, organic matter, CP, non-fiber carbohydrates, and total digestible nutrients. No differences were observed among treatments (P > 0.05) for average daily gain (X = 1.99 kg/day) and carcass traits. We conclude that it is possible to feed Holstein-Zebu crossed bulls with an average daily gain of approximately 2 kg using a fixed level of 11 % CP during the entire feedlot period, and this diet is economically viable and environmentally sound.