Effects of Implant Programs on Buller Incidence, Feedlot Performance, and Carcass Characteristics of Yearling Steers

Abstract

English and English × Continental crossbred steers (272 steers per pen; 4 pens per treatment) were used in a randomized complete block design to determine the effects of terminal implant type (Revalor S® [Hoechst-Roussel Vet, Somerville, NJ] and Component TES™ [Vet Life, Overland Park, KS]; each containing 24mg of estradiol-17β and 120mg of trenbolone acetate) and timing of terminal implant administration (d 1 or 50) on buller incidence, feedlot performance, and carcass characteristics. Steers either received Component TES™ (TES) or Revalor S® (RevS) on d 1 or 36mg of zeranol (Ralgro®; Schering-Plough, Omaha, NE) on d 1 and TES (Ral/TES) or RevS (Ral/RevS) on d 50. Steers receiving TES and RevS were not removed from the home pen on d 50, and all steers were harvested after 144 d. Bullers pulled during the first 50 d were returned to home pens on d 50 and were classified as a repull if removed again as a buller. The incidence of new bullers during the first 50 d did not differ (P=0.14) between steers receiving TES (2.3%), RevS (1.75%), or Ralgro® initially (1.42%; Ral/TES + Ral/RevS). There were fewer new bullers from d 50 to 144 for TES and Ral/TES than for RevS and Ral/RevS (P=0.02; 0.97% vs 1.88%, respectively) and also when steers received a terminal implant on d 1 compared with d 50 (P=0.01; 0.92% vs 1.93%, respectively); however, the overall incidence of new bullers did not differ (P>0.43) among treatments. Neither implant type nor timing influenced repull incidence from d 50 to 144 (P>0.45) or the overall incidence of total (new + repull) bullers (P>0.43). Steer DMI (implant type × timing, P=0.04) was least (P<0.02) for Ral/TES, intermediate for TES, and greatest RevS and Ral/RevS. Live and carcass-adjusted BW gain efficiencies were 2.4% greater (P<0.03) for TES or Ral/TES than for RevS or Ral/ RevS. Final BW, ADG, and hot carcass weight did not differ (P>0.19) among treatments. Steers receiving Ral/TES and Ral/RevS had a greater percentage of dark cutters (P<0.01), more Yield Grade 1 carcasses (P<0.01), and fewer Yield Grade 3 carcasses (P<0.01) than TES or RevS. Administering TES on d 1 or 50 resulted in improved gain efficiency, whereas overall buller incidence was not influenced by terminal implant type or timing. Administering either TES or RevS on d 50 increased the incidence of dark carcasses, resulted in more Yield Grade 1 and fewer Yield Grade 3 carcasses, and influenced when bullers developed but did not influence carcass quality grade distribution or overall buller incidence.