Abstract
The objectives of the study were to determine the effect of coated or noncoated hormone implants on growth performance, carcass characteristics, and serum estradiol-17β (E(2)) concentrations of Holstein steers fed a grain-based diet for 112 d. Seventy-nine Holstein steers [average initial body weight (BW) = 452 ± 5.5 kg] were stratified by BW and allotted to one of two treatments: 1) Holstein steers implanted with a coated implant containing 200 mg of trenbolone acetate (TBA) and 40 mg E(2) (Revalor-XS (Merck Animal Health; Summit, NJ)] on day 0 (XS) or 2) Holstein steers implanted two times (days 0 and 56) with a noncoated implant containing 80 mg of TBA and 16 mg of E(2) [(2IS) Revalor-IS (Merck Animal Health)]. Data were analyzed using the MIXED procedure of SAS (SAS Inst. Inc., Cary, NC). There was no effect (P ≥ 0.71) of implant strategy on initial, middle, and final BW. No effect (P ≥ 0.12) of implant strategy was observed on average daily gain, dry matter intake, or gain-to-feed ratio. There were no effects (P ≥ 0.11) of implant strategy on carcass characteristics. There was an implant × day interaction (P < 0.01) for the circulation of serum E(2) concentrations. Serum E(2) concentration increased similarly 14 d after Holstein steers were implanted, regardless of implant strategy. At 28 d, after steers were implanted, steers in the XS group had less serum E(2) concentration than Holstein steers in the 2IS group. However, at 56 d after the first implantation, both groups, once again, had similar serum E(2) concentrations and E(2) concentrations were less on day 56 than day 28 for both strategies. Holstein steers implanted with 2IS had greater serum E(2) concentration on day 70 and E(2) concentrations remained greater than serum E(2) of Holstein steers implanted XS for the duration of the trial (day 112). In summary, there was no effect of coated or two doses of noncoated implant on growth performance or carcass characteristics of Holstein steers.