Evaluation of coated steroidal combination implants on feedlot performance and carcass characteristics of beef heifers fed for constant or varying days on feed

Two experiments evaluated the effects of delayed, long-lasting implant strategies for finishing heifers fed constant or varying days on feed. In Exp. 1, (n = 500; initial BW 280 ± 21 kg) were allotted randomly to 1 5 treatments, including no (CON), Revalor-XH d (XH), Revalor-200 (E200), Revalor-XR (XR), 70 (D200). All implants contained 200 mg trenbolone acetate and 20 estradiol. 2, 720 (initial 281 10 assigned treatments in a 3 × 4 factorial arrangement, with [no (NCON), 100 (PCON), (XH)] serial slaughter dates following 151, 165, 179, 193 implanted heavier, gained more, more efficient (P ? 0.03) compared CON heifers, but differences observed among ? 0.21) over 198-d trial. Implanted had greater hot carcass weight lower marbling scores 0.04). there treatment interactions growth performance 0.23) characteristics 0.31). Final BW, fat thickness, numerical YG increased linearly < 0.01), whereas ADG 0.01) G:F 0.02) decreased linearly, increasing Hot was by implanting strategy feed, aggressive did not improve performance.