Effect of Trace Mineral Supplementation with or without Hormone Implants on Growth and Carcass Characteristics of Steers

To determine the effects of trace mineral (TM) supplementation and hormone implant strategy on growth and carcass characteristics of cattle, 72 Angus-cross steers (388 ± 17 kg) were blocked by BW (6 steers per pen) to a 2 x 3 factorial. Steers were either implanted (d 0 with Component TE-IS, reimplanted d 56 with Component TE-200; IMP) or not (NoIMP). Within implant treatments cattle received no supplemental TM (CON), TM supplemented at 2016 NRC recommendations of 10 Cu, 30 Zn, 20 Mn, 0.10 Se, 0.15 Co, and 0.50 I (mg/kg; NRC), or TM supplemented at feedlot consultant recommendations of 20 Cu, 100 Zn, 50 Mn, 0.30 Se, 0.20 Co, and 0.50 I (mg/kg; IND). Blood samples were collected on d -7, 70 and 124. Steers received a finishing diet for 124 d in GrowSafe bunks and were harvested on d 125. Data were analyzed in SAS as a 2 × 3 factorial with the fixed effect of block, and steer as experimental unit (n = 12 per combination). Day -7 glucose concentrations were used as a covariate in analysis. There was a tendency (P = 0.06) for an IMP × TM for d 124 plasma glucose with NoIMP/NRC being greater than NoIMP/IND and all other treatments intermediate. There were no IMP × TM for final BW, overall ADG, DMI, G:F, dressing percent, backfat, marbling score, or KPH (P ≥ 0.17). Overall ADG tended (P = 0.07) to be and HCW was (P = 0.03) affected by TM, where IND was greater than CON (HCW: 373, 378, and 388 kg for CON, NRC, and IND, respectively). Overall DMI was increased by TM (P < 0.0001) with NRC and IND being greater than CON. Steers receiving implants had greater (P < 0.0001) final BW (559 and 617 kg for NoIMP and IMP, respectively), overall ADG (1.35 and 1.83 kg for NoIMP and IMP, respectively), DMI, G:F, and HCW (359 and 400 kg for NoIMP and IMP, respectively) than NoIMP. There was an IMP × TM (P = 0.02) for ribeye area (REA) with IMP/CON having greater REA than IMP/IND, with IMP/NRC being intermediate; NoIMP had smaller REA, regardless of TM supplementation. There was an IMP × TM (P = 0.02) for YG where NoIMP/IND was greater than IMP/CON with all other treatments intermediate. These data indicate NRC TM recommendations might not be adequate for finishing beef steers, irrespective of hormone implant administration.