Effects of Revalor-XH, Revalor-200, and combination Revalor-IH/Revalor-200 on yearling beef heifer growth performance and carcass characteristics for 138 days on feed

Abstract

The objective was to evaluate finishing heifer implant programs including a single noncoated implant (Revalor-200; REV-200); an initial noncoated implant (Revalor-IH) followed by another noncoated implant (Revalor-200; REV-IH/200) 80 d before slaughter; or a partially coated, delayed-release implant (Revalor-XH; REV-XH) on growth performance and carcass characteristics when heifers were fed for 138 d. A commercial feedlot trial used 1,728 crossbred heifers (initial BW = 412 kg; SD = 28.2 kg) to examine the 3 implant strategies. Only heifers implanted with REV-IH/200 were removed from their pen at re-implantation. Heifers implanted with REV-IH/200 had greater (P ≤ 0.05) carcass-adjusted final BW, calculated as hot carcass weight/DP, and G:F compared with heifers implanted with REV-200 or REV-XH. Treatment did not affect (P ≥ 0.24) final BW or ADG on a live basis. Heifers implanted with REV-IH/200 had greater (P ≤ 0.05) hot carcass weight and LM area compared with heifers implanted with REV-200 or REV-XH. Marbling score and 12th-rib fat thickness were not different (P ≥ 0.12) among implant treatments. Calculated YG were decreased (P = 0.05) for heifers implanted with REV-IH/200 compared with heifers implanted with REV-200, with a significant (P < 0.01) shift to a lower calculated YG distribution for heifers implanted with REV-IH/200 compared with REV-200 or REV-XH. Greater concentrations of trenbolone acetate and estradiol-17β improved carcass-adjusted G:F and hot carcass weight but did not significantly decrease marbling despite heifers having a lower calculated YG.