Effects of Levels and Sources of Protein on Performance and Carcass Characteristics of Steers Fed All-Concentrate Rations

Abstract

Two finishing and two metabolism studies were conducted to determine effects of levels and sources of protein on feedlot performance, carcass characteristics, ration digestibility and nitrogen balance of steers fed all-concentrate, sorghum-grain rations of sorghum grain alone, sorghum grain plus 1% urea, or sorghum grain plus soybean meal isonitrogenous to 1% urea. Protein content of the all sorghum grain diet was 9.55% in the first finishing trial and 8.40% in the second. In the first finishing trial steers fed the all-sorghum grain ration did not consume sufficient sorghum grain to meet their protein requirement, gained less (P<.05) and were less efficient than those receiving urea or soybean meal. Steers on the all-sorghum grain ration were under-finished at slaughter (155 days). Feed consumption was greater in the second finishing trial, so minimum protein requirements were met on all treatments. No significant differences were observed for performance or carcass characteristics. Apparent protein digestibility was increased when urea and soybean meal were added to the rations, nitrogen retention was not significantly altered but favored the soybean meal supplemented ration in both metabolism trials.