Evaluating the effects of an injectable trace mineral product on steers raised in a natural beef feedlot program

Abstract Text: To determine effects of an injectable trace mineral (TM) on growth and TM status of steers fed in a natural program 168 certified natural Angus steers (359 ± 36.6 kg), blocked by BW (6 steers per pen), received an injection of sterilized saline (SAL) or Multimin90 (MM) on d 0 at 1 mL/68 kg BW (n = 14 pens, 84 steers per treatment). Multimin90 contains 15 mg Cu, 60 mg Zn, 10 mg Mn, and 5 mg Se/mL. Steers received a growing diet for 56 d, followed by 3 weeks of transition. On d 84 steers started a corn-based finishing diet and received a second injection of SAL or MM, creating four treatments (n = 7 pens, 42 steers per treatment): 1) d 0 Saline, d 84 Saline (SAL/SAL); 2) d 0 Saline, d 84 Multimin90 (SAL/MM); 3) d 0 Multimin90, d 84 Saline (MM/SAL); and 4) d 0 Multimin90 and d 84 Multimin90 (MM/MM). Blood and liver mineral concentrations were determined (n = 7 per treatment) on d -5, 14, 79, and 98. Steers were harvested on day 162. Data were analyzed in SAS with the fixed effects of block and treatment (2 treatments for growing, 4 treatments for finishing), with mineral data as repeated measures. Steer was experimental unit except for DMI and G:F, where experimental unit was pen. Treatment did not affect growing or finishing ADG, DMI, or G:F (P  ≥  0.14). There was a treatment × day interaction for finishing period ADG (P = 0.01), where ADG was similar across treatments from d 84 to 113, and greatest in SAL/SAL from d 113 to 144; however, MM/MM was greatest from d 140 to 161. There was a treatment × day interaction for liver Se (P < 0.001), where concentrations increased on d 14 in MM-treated steers, were similar across treatments on d 79, but increased on d 98 in SAL/MM and MM/MM. Liver TM concentrations tended (P = 0.08) to display treatment × day interactions where MM/MM had greater Mn and Cu on d 14, tended to have greater liver Mn and Cu than MM/SAL and SAL/SAL on d 79, and had greater liver Cu compared to SAL/SAL and MM/SAL on d 98. Adequate steer TM status at onset of this trial likely negated any potential benefits of injectable minerals and injectable TM can be utilized safely in natural finishing programs.

Keywords: beef, natural, mineral