The effects of injectable trace minerals on growth performance and mineral status of Angus beef steers raised in a natural feedlot program

To evaluate the effects of an injectable trace mineral (TM) on TM status and growth of feedlot steers raised in a Certified Angus Beef Natural system, 168 certified natural Angus steers (359 ± 36.6 kg), blocked by initial BW into pens of 6 head, received a sterilized saline (SAL, n = 84) or Multimin90 (ITM, n = 84) injection (1.47 mL/100 kg of BW). Steers were grown on a corn silage–based diet for 56 d and transitioned, and on d 84 they began a dry-rolled corn–based finishing diet. On d 84 steers were assigned equally within treatment, SAL or ITM, to receive a second injection, making 4 total treatments: (1) d 0 SAL, d 84 SAL (SAL/SAL, n = 42); (2) d 0 SAL, d 84 ITM (SAL/ITM, n = 40); (3) d 0 ITM, d 84 SAL (ITM/SAL, n = 40); and (4) d 0 ITM, d 84 ITM (ITM/ITM, n = 42). Liver Cu and Se concentrations were greater (P ≤ 0.01), and liver Zn concentrations tended (P = 0.07) to be greater in ITM versus SAL steers on d 14. Liver Zn and Mn were not different on d 98 (P ≥ 0.64). Liver Cu (P = 0.02) and Se (P < 0.001) concentrations were greater in SAL/ITM and ITM/ITM on d 98. Injectable TM had no effect on growing or finishing BW or G:F (P ≥ 0.14). Steers had adequate TM status throughout the trial, likely explaining the lack of performance differences due to TM treatment.