116 Effect of Coated and Non-coated Steroidal Implants on Growth Performance, Dietary Net Energy Utilization and Carcass Traits of Feedlot Finishing Steers

Abstract

\n Maine-Anjou x Angus steers (n = 156, initial BW 366 ± 37.2 kg) were used in a 132-d finishing experiment at the Ruminant Nutrition Center in Brookings, SD. Steers were weighed on two consecutive days and assigned into 5 weight blocks. Within each weight block steers were randomly assigned to two implant types (equal steroidal hormone dose; both from Zoetis, Parsippany, NJ) and two dietary treatments in a 2 × 2 factorial arrangement. Implant treatments consisted of 1) Coated implant, 200 mg trenbolone acetate (TBA), 28 mg estradiol benzoate (EB) (Synovex ONE Feedlot, ONE) or 2) Non-coated implant, 200 mg TBA, 28 mg EB (Synovex PLUS; PLUS), placed in the left ear. Dietary treatments were 1) 15% or 2) 30% corn silage (DM basis). No interaction between implant and corn silage inclusion was observed for carcass-adjusted (hot carcass weight / 0.63) growth performance, dietary net energy (NE) utilization or carcass traits (P ≥ 0.16). Bunks were managed using a slick bunk approach and all diets contained (DM basis) 33 mg/kg monensin sodium. Implant status was checked on d 28 by a single trained evaluator; steers with missing implants were immediately re-implanted. There was no difference in carcass-adjusted growth performance between implants (P ≥ 0.85). There were no differences in observed NE or the observed-to-expected ratio of NE for either growth or maintenance (P ≥ 0.90). No differences were observed for dressing percent, hot carcass weight, ribeye area, or rib fat (P ≥ 0.22). Marbling differed between implant treatments (433 to 466 ± 8.7; P = 0.01) for PLUS and ONE respectively. Implanting cattle with a coated implant had no detrimental effect on growth performance or carcass traits, but it did increase marbling scores.