Effects of using increasingly aggressive implant protocols on feedlot performance and carcass characteristics of calf-fed steers

Three experiments evaluated aggressive implant strategies to better understand implant duration and allow for maximum return on implant investment in feedlot steers. Crossbred steers (n = 1,350; 282 kg initial BW, SD = 8) were fed for an average of 215 d (Exp. 1). Treatments were Revalor-IS (80 mg of trenbolone acetate and 16 mg of estradiol) or Revalor-XS (200 mg of trenbolone acetate and 40 mg of estradiol) initially followed by 1 or 2 consecutive Revalor-200 (200 mg of trenbolone acetate and 20 mg of estradiol) implants (6 replications). Crossbred steers (n = 1,513; 265 kg initial BW, SD = 18) were fed for an average of 208 d (Exp. 2). Treatments were (1) Revalor-G (40 mg of trenbolone acetate and 8 mg of estradiol) on d 0, Revalor-IS on d 50, and Revalor-200 on d 140; (2) Ralgro (36 mg of zeranol) on d 0 and Revalor-XS on d 50; and (3) Revalor-XS on d 0 and Revalor-200 on d 140 (5 replications). Holstein steers (n = 1,832; 144 kg initial BW, SD = 11) were fed for an average of 360 d (Exp. 3). Treatments were (1) Ralgro on d 0, Revalor-IS on d 120, and Revalor-S on d 240; (2) Ralgro on d 0 and Revalor-XS on d 120; (3) Ralgro on d 0, Revalor-IS on d 60, and Revalor-XS on d 160; and (4) Revalor-XS on d 0 and Revalor-XS on d 160 (6 replications). In all 3 experiments, final BW, ADG, and HCW were not affected by treatment (P ≥ 0.12). Increasingly aggressive implant protocols have limited effects on feedlot and carcass performance of beef and Holstein steers.