Performance of finishing beef steers in response to anabolic implant and zilpaterol hydrochloride supplementation

S. L. Parr, K. Y. Chung, M. L. Galyean, J. P. Hutcheson, N. di Lorenzo, K. E. Hales, M. L. May, M. J. Quinn, D. R. Smith, B. J. Johnson

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


Our objectives were to evaluate the dose/payout pattern of trenbolone acetate (TBA) and estradiol-17β (E 2) 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). The main effects of treatment were implant [no implant (NI); Revalor-S (REV-S; 120 mg of TBA + 24 mg of E 2); and Revalor-XS (REV-X; 200 mg of TBA + 40 mg of E 2)] 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 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 E 2 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. REVS. 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 ZH (19-kg difference) and implant, with REV-X resulting in the greatest response (HCW of 376 for NI vs. 404 and 419 kg 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 + E 2 and extended payout improved steer performance and HCW.

Original languageEnglish
Pages (from-to)560-570
Number of pages11
JournalJournal of animal science
Issue number2
StatePublished - Feb 2011


  • Beef steer
  • Estradiol-17β
  • Trenbolone acetate
  • Zilpaterol hydrochloride


Dive into the research topics of 'Performance of finishing beef steers in response to anabolic implant and zilpaterol hydrochloride supplementation'. Together they form a unique fingerprint.

Cite this