Short communication: Comparison of long-acting or conventional growth implants on growth performance in steers grazed for 180 days

Abstract

Steers are often implanted with androgenic and/or estrogenic hormones to repartition nutrients to increase protein synthesis while increasing feed efficiency and profitability. Long-acting implants with 200 d of activity are available that may simplify multi-implant regimens and reduce labor costs and cattle handling. The purpose of this study was to determine if steers grazing wheat pasture for 180 d and implanted with a long-acting implant containing 150 mg trenbolone acetate and 21 mg estradiol benzoate in a novel, coated formulation (Synovex ONE Grass [SYN]) would increase growth performance compared to steers implanted with either Ralgro (RAL) or Revalor G (REV-G). Crossbred beef steers (n = 345; BW = 252 ± 1.9 kg) were stratified by BW and allocated randomly to 1 of 3 implant treatments (SYN, RAL, or REV-G) based on d -1 BW in a completely randomized design. On d 0, calves were administered the treatment implant according to label. Steers were grazed as a single group and rotated according to forage availability for 180 d on wheat pastures. Body weights were recorded on d -1, 0, 90, 180, and 181. Data were analyzed using the MIXED procedures of SAS with calf serving as the experimental unit with significance declared at P ≤ 0.05. Final BW were not different (P = 0.26; SE = 2.7 kg) between treatments; however, BW were numerically greater in SYN (406 kg) steers compared to RAL (400 kg) and REV-G (401 kg) steers. Average daily gain from d 0 to 90 tended to be greater (P = 0.08) in RAL and REV-G steers compared to SYN. Synovex ONE Grass (1.14 kg/d) ADG from d 90 to 180 was greater (P < 0.0001; SE = 0.02) compared to RAL (1.02 kg/d) or REV-G (1.04 kg/d) steers. Overall, ADG tended to be greater (P = 0.06) in SYN implanted steers compared to RAL and REV-G. The use of SYN improved steer growth performance from d 90 to 180 while BW were not affected by implant for the duration of the 180-d study in steers grazing wheat pasture.