ARS | Publication request: EFFECTS OF DIETARY CRUDE PROTEIN LEVEL AND DEGRADABILITY ON PERFORMANCE AND CARCASS CHARACTERISTICS OF GROWING-FINISHING BEEF STEERS.

Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: April 22, 2003
Publication Date: June 22, 2003
Citation: Gleghorn, J. F., Elam, N. A., Galyean, M. L., Duff, G. C., Cole, N. A. Effects of Dietary Crude Protein Level and Degradability on Performance and Carcass Characteristics of Growing-Finishing Beef Steers. Journal of Animal Science. 2003. v. 81(Suppl.1). p. 109. Abstract No. 433.

Technical Abstract: Two experiments were conducted at two locations to determine the effects of dietary CP level and source on performance and carcass characteristics of beef steers. British x Continental steers were blocked by BW (357 ± 28 and 305 ± 25 kg initial BW; n=360 and 225; four and five pens/treatment in Exp. 1 and 2, respectively). Steam-flaked corn-based diets were arranged in a 3 x 3 factorial with three CP levels (11.5, 13, 14.5% of DM) and three sources of supplemental CP (N basis): 100% urea (U), 50:50 blend of urea and cottonseed meal (B), or 100% cottonseed meal (C). Steers in both experiments were initially implanted with Ralgro and reimplanted with Revalor-S on d 56. Performance and carcass data were pooled over location and analyzed with mixed model procedures using pen as the experimental unit. Crude protein level quadratically affected ADG (P < 0.05) and carcass-adjusted (to a common dress) ADG (P < 0.10). Increasing the level of supplemental urea linearly increased carcass-adjusted ADG and gain:feed (P < 0.05) and carcass-adjusted gain:feed (P < 0.001). Dry matter intake was not affected by CP level or source (P > 0.10). Hot carcass weight (HCW) and longissimus muscle area (LMA) linearly increased with increasing urea level (P <. 0.05), whereas increasing CP level quadratically affected HCW and LMA (P < 0.06), with maximum values at 13% CP. Differences in dressing percent, back fat thickness, and yield grade were negligible across treatments. Neither marbling score nor percentage of carcasses grading Choice was affected by CP level or source. Results indicate that increasing CP levels from 11.5 to 13% slightly increased ADG and carcass-adjusted ADG, whereas increasing the proportion of supplemental urea increased carcass-adjusted ADG, gain:feed, carcass-adjusted gain:feed, HCW, and LMA. A CP level above 13% seemed to be detrimental to HCW and LMA.