The effect of different implant programs on beef × dairy steer feedlot growth performance and carcass characteristics

Abstract The objective of this study was to evaluate potency and timing of trenbolone acetate (TBA) administration on live performance and carcass characteristics of beef × dairy steers. A total of 6,895 beef × dairy steers [initial body weight (BW) = 157 ± 5.2 kg] were allotted into 30 pens, with pen as the experimental unit. Each pen was randomly assigned one of three implant treatments: 1) Revalor-IS (IS) at d 0, IS at d 80, and Revalor-XS (XS) at d 160 (IS/IS/XS); 2) Ralgro at d 0, IS at d 80, and XS at d 160 (Ral/IS/XS); or 3) Encore at d 0 and XS at d 160 (Enc/XS). Steers were blocked by arrival date, each pen was terminally sorted in three ways at 257 ± 22 days on feed and harvested at 329 ± 25 days on feed. For live and carcass outcomes, fixed effect of implant treatment and random effect of block was evaluated. Data are reported on a deads and removals out basis. Removals, morbidity, and mortality were similar (P ≥ 0.45). Steers administered TBA prior to d 160 were 5.8 kg heavier (P = 0.03) than Enc/XS steers at d 160. Final BW was not different (P = 0.78). Early administration of a TBA-containing implant resulted in an increased prevalence of bullers [2.40%, 5.18%, 6.86% (for Enc/XS, Ral/IS/XS, and IS/IS/XS) respectively; P