PS12-22. Impacts of Implant Type on Feedlot Performance, Feeding Behavior, Blood Metabolites, and Carcass Traits of Angus Steers.

Abstract The objective of this research was to determine how implant formulations differing in trenbolone acetate (TBA) and estradiol (E2) concentrations influence feedlot performance, feeding behavior, circulating metabolites, and carcass traits of finishing steers. E2 is thought to increase nutrient availability, while TBA directly promotes skeletal muscle growth. Evaluating different hormone concentrations together can help explain how these hormones work in concert to improve production efficiency. Sixty Angus steers (initial BW = 456.0 ± 8.7 kg) were fed for 144 d in four pens equipped with Vytelle bunks to measure intake and feeding behavior. Steers received one of four treatments: no implant (CON, n = 15), Compudose (E2; estradiol only, n = 15), Revalor-S (REVS; 120 mg TBA and 24 mg estradiol-17β, n = 15), or Revalor-200 (REV200; 200 mg TBA and 20 mg estradiol-17β, n = 15). Steers were fed a finishing ration typical for the region. Serum urea nitrogen (SUN), Beta-hydroxybutyrate (BHB), and lactate were measured on d 30, 60, and 90. Performance metrics such as dry matter intake (DMI), feeding behavior, body weight (BW), average daily gain (ADG) and feed efficiency (G:F) were collected on d 0, 30, 60, 90, 120, and 144. All carcass data were collected at harvest. Data were analyzed using the MIXED procedure of SAS with treatment as a fixed effect and pen and source of cattle as random variables. All implant treatments had increased (P ≤ 0.04) DMI compared to CON. Bunk visits (BV), bunk visit duration (BVDUR), feed bouts (FB), and feed bout duration (FBDUR) were all impacted by implant (P = 0.01), described by E2 having increased (P < 0.001) BV and FB but decreased (P < 0.001) BVDUR and FBDUR when compared to CON. Implanted cattle had increased (P ≤ 0.06) BW compared to CON, but G:F was not (P = 0.22) altered by implant. Circulating SUN was impacted by implant (P = 0.04), with REV200 and REVS generally lower than CON and E2. There were also differences in BHB (P = 0.03), with E2 and REVS generally having increased BHB concentrations compared to CON and REV200. Lactate and NEFA were not affected by implant (P ≥ 0.18). Hot carcass weight tended to differ (P = 0.08), with REV200 being greater (P = 0.05) than CON. No other carcass traits were impacted (P ≥ 0.20) by implant. Results indicate implant type altered intake behavior and select circulating metabolites alongside potential improvements in performance and carcass weight. This suggests implant differences in nutrient use and partitioning may help explain variation in production efficiency among implant strategies.