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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 body weight (six steers per pen) to a 2 x 3 factorial. Factors included growth-stimulating implant (GS): day 0 with Component TE-IS, reimplanted day 56 with Component TE-200 (IMP) or no implant (NoIMP), and TM supplementation (TM): no supplemental TM (CON), TM supplemented at national (NASEM, 2016). Nutrient requirements of beef cattle. 8 th ed. Washington, DC: The National Academics Press) recommendations of 10 Cu, 30 Zn, 20 Mn, 0.10 Se, 0.15 Co, and 0.50 I (mg/kg; REC), 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). Steers received a finishing diet for 124 d in GrowSafe bunks and were harvested on day 125. Data were analyzed in SAS as a 2 x 3 factorial with steer as the experimental unit (n = 12 per combination). Day -7 liver trace mineral concentrations were used as a covariate in analysis. There were no GS x TM effects for liver Zn, Mn, Se, or Co (P ≥ 0.11) on day 70 or 125. Implanted steers had lesser liver Cu and Mn on day 70 (P ≤ 0.05) and day 125 compared with NoIMP. There was a GS x TM interaction for liver Cu on day 125 (P = 0.05) where IMP/ REC, IMP/IND, and NoIMP/REC had greater liver Cu than NoIMP/CON, which had greater liver Cu than IMP/CON. There was a TM effect for liver Cu on day 70 (P < 0.01) with IND having greater liver Cu than REC and CON. There was a TM effect (P ≤ 0.01) for liver Mn and Se on day 70 where IND had greater Mn and Se than CON, with REC being intermediate. There was a TM effect (P < 0.01) on liver Mn on day 125 where IND had greater liver Mn than CON and greater (P < 0.01) liver Se than CON and REC on day 125, whereas day 125 liver Se was greater in REC vs. CON. Implanted steers had greater (P < 0.01) dry matter intake (DMI), final body weight (BW), overall average daily gain (ADG), G:F, and hot carcass weight (HCW) than NoIMP. Overall DMI was affected by TM (P < 0.01) with REC and IND being greater than CON. There was a TM effect for carcass-adjusted final BW, ADG, and DMI (P ≥ 0.03) and a tendency for TM to affect adjusted G:F (P = 0.07). There was a TM effect (P = 0.03) for HCW where IND was greater than CON and REC. There was a GS x TM (P = 0.02) for rib- eye area (REA); within IMP, CON were greater than IND, whereas REC were intermediate while NoIMP had smaller REA, regardless of TM supplementation. Additional research is needed to better determine trace mineral requirements of finishing beef steers for optimal performance. [ABSTRACT FROM AUTHOR]

A 169-d study utilizing 208 Angus-cross heifers (291 ± 23 kg; 4 sources) in a 2×2 factorial examined the effects of implant strategy and Zn supplementation on growth and mineral status of heifers. Factors included 2 implant (Merck Animal Health, Madison, NJ) strategies: extended-release Revalor-XH on d 0 (REV-XH; 20 mg estradiol+200 mg trenbolone acetate) or Revalor-200 on d 0 and 91 (REV-200; 20 mg estradiol+200 mg trenbolone acetate) and 2 supplemental Zn (mg/kg dry matter [DM]; ZnSO4) strategies: national (30; NRC) or industry (100; IND) recommendations. Heifers were blocked by weight within source (n = 5 or 6 heifers/pen; 9 pens/treatment), received a corn silage-based diet (d 0-56), then transitioned to a corn-based diet fed via concrete bunks. Data were analyzed in Proc Mixed of SAS; fixed effects of implant (IMP), Zn, interaction, and source with the repeated effect of time for average daily gain (ADG) and liver mineral. Initial weight served as a covariate for performance and carcass data. Revalor-200 had greater ADG from d 0-28 and 91-120, while REV-XH peaked during d 56-91 (IMP × time; P = 0.02), corresponding to likely periods of greatest hormone payout from each implant. Liver Mn concentrations decreased on d 14 regardless of implant while d 105 and 164 concentrations were lesser for REV-200 (IMP × time; P = 0.02). Hot carcass weight, DM intake, carcass-adjusted ADG and feed efficiency were not different between IMP strategies (P = 0.18). Steers fed IND tended to be heavier on d 91 (P = 0.06) and were heavier on d 120 (P = 0.05) than NRC; however, final BW did not differ due to Zn (P = 0.37). The similar performance between implant strategies and superior performance during peak hormone payout by heifers supplemented IND vs. NRC suggests increased Zn may support rapid growth. [ABSTRACT FROM AUTHOR]