Effects of trace mineral injections on measures of performance and trace mineral status of pre- and postweaned beef calves.

Three experiments were conducted to examine the effects of injectable trace minerals (ITM) on measures of trace mineral status and performance in pre- and postweaned Brangus-crossbred beef calves. In Exp. 1, calves were assigned to treatments in alternating birth order (n = 150; 75/treatment), consisting of a 1-mL subcutaneous injection of ITM (MultiMin 90; MultiMin USA, Inc., Fort Collins, CO) or sterile saline. The ITM formulation consisted of 60, 10, 15, and 5 mg/mL of Zn, Mn, Cu, and Se. Treatments were readministered at 100 and 200 d of age. Calf BW was recorded at birth and on d 100, 150, 200, and 250 (weaning). Trace mineral status was assessed in liver biopsy samples (n = 12/treatment) collected on d 150, 200, and 250. Administration of ITM had no impact on BW gain (P ≥ 0.55) but did result in greater (P ≤ 0.02) concentrations of liver Cu and Se and lesser (P = 0.05) liver Fe concentrations compared to saline-injected calves. In Exp. 2, 24 heifers were selected from the weaned calves of Exp. 1 (n = 12/treatment) and transported 1,600 km. Remaining on their original treatments, heifers were administered 5 mL of ITM or saline following transport (d 0). Blood samples, for acute phase protein (APP) analysis, were collected on d 0, 1, 3, 6, 9, and 13 and liver biopsy samples for assessment of trace mineral status on d 13. Plasma APP concentrations increased in all calves following weaning and transport but concentrations were greatest (P < 0.05) in ITM- vs. saline-injected heifers on d 6 and 9. Liver concentrations of Cu, Se, and Zn were greater (P ≤ 0.04) but ADG lesser (P = 0.05) for heifers receiving ITM vs. saline. In Exp. 3, 34 heifers, without previous exposure to ITM, were enrolled in a 177-d development study (n = 17/treatment). Treatments consisted of 2.5-mL injections of ITM or sterile saline on d 0, 51, and 127. Humoral immune response to an injection of porcine red blood cells (PRBC) was evaluated on d 51. Trace mineral status was evaluated in liver biopsy samples collected on d 177. Overall heifer ADG, PRBC antibody titers, and liver Se concentrations were greatest (P ≤ 0.06) for ITM vs. control heifers. Collectively, these studies demonstrate an increased trace mineral status, a greater humoral response to novel antigen, and a heightened APP response to weaning and transport stress in pre- and postweaned beef calves administered ITM.