Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract only
Publication Acceptance Date: 11/12/2009
Publication Date: 10/1/2010
Citation: Parr, S.L., Chung, K.Y., Galyean, M.L., Hutcheson, J.P., Dilorenzo, N., Hales, K.E., May, M.L., Quinn, M.J., Smith, D.R., Johnson, B.J. 2010. Performance of finishing beef steers in response to anabolic implant dose and zilpaterol hydrochloride. Journal of Animal Science Supplement. 88(E-Suppl. 3):131. Interpretive Summary:
Technical Abstract: British × Continental steers (n = 168; 7 pens/treatment; initial BW = 362 kg) were used to evaluate the dose of trenbolone acetate (TBA) and estradiol-17ß (E2) and feeding of zilpaterol hydrochloride (ZH) on performance and carcass characteristics. A randomized complete block design was used with a 3 × 2 factorial arrangement of treatments. Main effects were implant (no implant [NI]; Revalor-S [ REV-S; 120 mg TBA + 24 mg E2]; and Revalor-XS [REV-X; 200 mg TBA + 40 mg E2]) and ZH (0 or 8.3 mg/kg of DM for 20 d with a 3-d withdrawal before harvest). Steers were fed for 153 or 174 d depending on block. No implant × ZH interactions occurred for cumulative performance data. Overall final BW (591, 632, and 650 kg for NI, REV-S and REV-X, respectively), ADG (1.4, 1.7, and 1.8 kg) and G:F (0.16, 0.18 and 0.19) were increased (P < 0.05) as TBA and E2 dose increased. Implanting increased (P < 0.05) DMI, but DMI did not differ (P > 0.10) for REV-S and REV-X (8.8 for NI vs. 9.4 kg/d for the 2 implants). From d 1 to 112 of the feeding period, implanting increased (P < 0.05) ADG and G:F, but REV-S and REV-X did not differ (P > 0.10). From d 112 to end, ADG was increased (19%; P < 0.05) and G:F was greater (18%; P < 0.05) for REV-X vs. REV-S. Carcass-adjusted final BW (614 vs. 643 kg for 0 and 8.3 mg/kg ZH respectively), ADG (1.5 vs. 1.7 kg/d), and G:F (0.17 vs. 0.19) were increased (P < 0.05) by ZH. Hot carcass weight was increased (P < 0.05) by both ZH (390 vs. 409 kg) and implant, with REV-X resulting in the greatest response (376 for NI vs. 404 and 419 for REV-S and REV-X respectively; P < 0.05). An implant × ZH interaction (P = 0.05) occurred for dressing percent (DP). Without ZH, implanting increased DP, but DP did not differ (P > 0.10) for REV-X and REV-S. With ZH, REV-X increased (1.7%; P < 0.05) DP vs. NI and REV-S. Marbling score, 12th-rib fat, and KPH were not affected (P > 0.10) by implant or ZH. A greater dose of TBA and E2 in combination with ZH increased HCW and steer performance in an additive manner, suggesting a different mechanism of action for ZH and steroidal implants.