Animal Sciences Commons^™

Effects Of Beef Production System On Animal Performance And Carcass Characteristics, C. L. Maxwell, C. R. Lopez, B. K. Wilson, B. T. Johnson, B. C. Bernhard, C. F. O'Neill, D. L. Vanoverbeke, G. G. Mafi, D. L. Step, C. J. Richards

Department of Animal Science: Faculty Publications

The objective of this study was to evaluate conventional (CONV) and natural (NAT) beef production systems from annual pasture through finishing through grazing. Beef steers (n = 180, initial BW = 250 ± 19 kg) were assigned randomly to 2 treatments in the pasture phase. Steers were implanted with 40 mg of trenbolone acetate (TBA), 8 mg estradiol, and 29 mg tylosin tartrate (CONV), or received no implant (NAT). Steers on the 2 treatments grazed wheat or cereal rye for 109 d. Conventional steers had an 18.5% improvement in ADG (1.22 vs. 1.03 kg/d, P < 0.01) and a heavier final BW (385 vs. 366 kg, P < 0.01) compared with NAT steers. Following the pasture phase, steers (n = 160 steers, 5 steers/pen, 8 pens/treatment) were assigned to a 2 × 2 factorial in the feedlot phase. Production system (NAT vs. CONV) was maintained from the pasture phase, and the second factor was 7 vs. 12% low-quality roughage (DM basis, LOW vs. HIGH). During finishing, CONV steers were given 120 mg of TBA and 24 mg estradiol at processing, fed monensin and tylosin, and fed zilpaterol hydrochloride for the last 20 d of the experiment. There were no program × roughage level interactions (P > 0.07). The CONV steers ate …