ARS | Publication request: Performance of finishing beef steers in response to anabolic implant and zilpaterol hydrochloride supplementation

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 7, 2010
Publication Date: January 1, 2011
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. 2011. Performance of finishing beef steers in response to anabolic implant and zilpaterol hydrochloride supplementation. Journal of Animal Science. 89:560-570.

Interpretive Summary: Recently, two new products, Revalor-XS (Intervet Schering Plough Animal Health, DeSoto, KS) and zilpaterol hydrochloride (ZH; Intervet Schering Plough Animal Health), have been approved for use in finishing cattle. Revalor-XS contains a special coating which results in a gradual, sustained release rate of trenbolone acetate (TBA) and estradiol-17b (E2) compared with the typical biphasic release rate demonstrated by uncoated cholesterol-based implant pellets, and thereby, eliminates the need to reimplant cattle. Although combining anabolic implants and ZH should improve carcass lean yield, the combination could reduce quality grade. Therefore, our objectives were to evaluate the dose/payout pattern of TBA and E2 implants and feeding of zilpaterol hydrochloride on performance and carcass characteristics of finishing beef steers. Treatments were 1) no implant; 2) Revalor-S implant (REV-S); and 3) Revalor-XS (REV-X) with ZH. Overall, shrunk final body weight, average daily gain and feed efficiency increased as TBA and E2 dose increased. Implanting increased dry matter intake, but dry matter intake did not differ between REV-S and REV-X implants. For the first half of the feeding period, implanting increased average daily gain and feed efficiency, but REV-S and REV-X did not differ. For the last half of the feeding period, average daily gain increased by 19% and feed efficiency was 18% greater for REV-X vs. REV-S implants. Final body weight, average daily gain, and feed efficiency were increased by ZH, but daily dry matter intake was not affected by feeding ZH. Overall, treatment increased steer performance and HCW in an additive fashion, suggesting different mechanisms of action for ZH and steroidal implants. In addition, a greater dose of TBA plus E2 and extended payout improved steer performance.

Technical Abstract: Our objectives were to evaluate the dose/payout pattern of trenbolone acetate (TBA) and estradiol-17b (E2) implants and feeding of zilpaterol hydrochloride (ZH) on performance and carcass characteristics of finishing beef steers. A randomized complete block design was used with a 3 × 2 factorial arrangement of treatments. British × Continental steers (n = 168; initial BW = 362 kg) were blocked by BW and allotted randomly to 42 pens (7 pens/treatment; 6 pens/block; 4 steers/pen). Main effects of treatment were implant (no implant [NI]; Revalor-S [REV-S; 120 mg of TBA + 24 mg of E2]; and Revalor-XS [REV-X; 200 mg of TBA + 40 mg of E2]) and ZH (0 or 8.3 mg/kg of DM for 20 d with a 3-d withdrawal before slaughter). Blocks were split into 2 groups, and block groups were fed for either 153 d or 174 d. No implant × ZH interactions were noted for cumulative performance data. Overall, shrunk final BW (567, 606, and 624 kg for NI, REV-S, and REV-X, respectively), ADG (1.25, 1.51, and 1.60 kg) and G:F (0.14, 0.16, and 0.17) increased (P < 0.05) as TBA and E2 dose increased. Implanting increased (P < 0.05) DMI, but DMI did not differ (P > 0.10) between 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 increased by 19% (P < 0.05) and G:F was 18% greater (P < 0.05) for REV-X vs. REV-S. Carcass-adjusted final BW (29-kg difference), ADG (0.2-kg/d difference), and G:F (0.02 difference) were increased (P < 0.05) by ZH, but daily DMI was not affected by feeding ZH. Hot carcass weight was increased (P < 0.05) by both ZH (19-kg difference) and implant, with REV-X resulting in the greatest response (HCW of 376 for NI vs. 404 and 419 lb 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) between 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. Overall, treatment increased steer performance and HCW in an additive fashion, suggesting different mechanisms of action for ZH and steroidal implants. In addition, a greater dose of TBA+ E2 and extended payout improved steer performance and HCW.