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The objective of this study was to determine the relative effects of stocker-phase implant strategies on growth and carcass characteristics of beef steers. In each of 2 locations (OK and MS), steers were grazed on cool-season annual pastures in fall 2018 through spring 2019. Steers (n = 300 in MS, n = 240 in OK) were randomly assigned to one of three implant treatments, 1) a single Synovex® One Grass implant at d 0, 2) a single Component® TE-G with Tylan implant at d 0, or 3) a reimplant treatment receiving Component® TE-G with Tylan at d 0 and again at d 82 (OK) or 85 (MS). Steers from each treatment were commingled in 2 (OK) or 3 (MS) pastures for 159 (OK) or 161 d (MS). Following grazing, steers were shipped to a commercial feedyard for finishing, sorted into 3 pens based on BW with each treatment equally represented in each pen, and were managed according to that site's BMPs. Steers from all treatments were implanted identically in the feedyard. Steers were slaughtered when the pen was visually estimated to be at 1 cm backfat. Carcass data of individuals were collected by camera grading equipment in the packing plant. Data were analyzed as a completely random design with animal as the experimental unit, treatment as a fixed effect, and pasture within location as a random effect. Marbling score tended to be greater in the single Component® TE-G with Tylan (treatment 2) vs. the other 2 treatments (425 vs 408 and 410, P = 0.07). No other production variables, including stocker-phase ADG, approached a significant difference (P > 0.39). No evidence was found to recommend stocker-phase reimplanting even in relatively long stocker phases with high ADG, and producers should consider selecting the most cost-effective implant at grazing initiation. [ABSTRACT FROM AUTHOR]

Data from three large-pen feedlot studies were pooled to evaluate use of a long-acting implant (Revalor-XS) as an initial implant in a re-implant program. The three studies consisted of 2,764 steers in 40 pens, with an initial body weight (BW) of 271 kg. Treatments consisted of Revalor-IS [80 mg trenbolone acetate (TBA), 16 mg estradiol (E2)] administered on arrival, followed by Revalor-200 (200 mg TBA, 20 mg E2) terminal implant (IS/200) or Revalor-XS (80 mg TBA, 16 mg E2 uncoated; 120 mg TBA, 24 mg E2 coated; 200 mg TBA, 40 mg E2 total) on arrival followed by Revalor-200 terminal implant (XS/200). Steers were fed to equal days-on-feed (DOF) within study and averaged 210 DOF. Steers within treatment were re-implanted at same DOF in two studies (Day 124 on average followed by an 81-day terminal implant window). In the third study, IS/200 steers were implanted on Day 120 and XS/200 steers on Day 140 of the 217-day study. Final BW averaged 635.6 and 638.3 kg for IS/200 and XS/200, respectively (P = 0.21). There were no differences (P > 0.26) in DMI, ADG and Gain:Feed between treatments. Hot carcass weight tended (P = 0.07) to be greater with XS/200 (412.7 kg) compared with IS/200 (409.1 kg). Ribeye area was greater (P < 0.01) and fat thickness tended (P = 0.06) to be lower with XS/200 compared with IS/200. Distributions of USDA quality grades were not affected (P = 0.26) by treatment. Distributions of USDA yield grades (YG) were affected (P = 0.01) by treatment with a shift toward more YG 1 and 2 carcasses with XS/200 and more YG 4 and 5 carcasses with IS/200. This analysis indicates that using Revalor-XS as an initial implant leads to greater carcass weight and ribeye area and lower YG when compared with Revalor-IS. [ABSTRACT FROM AUTHOR]