Dual Implantation of Feedlot Steers with Commercial Estradiol and Trenbolone Acetate Implants

Abstract

Recent introduction of the trenbolone acetate (TBA, Finaplix, Hoechst-Roussel Agri-vet Co., Somerville, NJ) implant into the U.S. market has stimulated interest in additive performance by implanting TBA along with commercial estradiol (E2) implants. Crossbred steers (Bos taurus; n = 168; initial wt = 759 lb) were implanted with one of six treatments in a 2 × 3 factorial arrangement with four pens of seven steers per treatment. The factors were: 0 (without) or TBA implant and either 0, STEER-oid (ST) or Synovex-S (SS), which are E2 based implants. Trenbolone acetate was reimplanted at 63 d. Steers were fed a steam-flaked grain sorghum based finishing diet for 115 or 153 d (final wt = 1100 lb). No interactions existed (P > 0.1) between TBA and E2 treatments over the experiment. Trenbolone acetate improved average daily gain (ADG; 2.68 vs. 2.44 lb, P < 0.01) and gain efficiency (lb gain/100 lb dry matter intake; 15.8 vs. 14.0, P < 0.001) over non-TBA implanted cattle. The ST and SS increased ADG (2.64 and 2.77 vs. 2.27 lb, P < 0.001), dry matter intake (15.1 and 15.8 vs. 13.8 lb/d, P < 0.05) and gain efficiency (15.1 and 15.8 vs. 13.8) over non-E2 implanted steers. Average daily gain for the SS steers tended to be greater (P = 0.09) than for ST steers. Trenbolone acetate addition improved ADG 13% (P < 0.05), 11% (P = 0.11) and 6% (P < 0.05) compared to non-E2, ST, and SS implanted steers, respectively. The response to all implant treatments declined after 115 d on trial. Carcass characteristics did not differ (P > 0.1) among treatments. Implantation with either ST of SS improved performance over nonimplanted steers and dual implantation with TBA and ST or SS improved steer performance over either implant alone.