Impact of a trace mineral injection at weaning on growth, behavior, and inflammatory, antioxidant, and immune responses of beef calves.

Two experiments evaluated the effects of an injectable trace mineral (ITM) solution at weaning on trace mineral (TM) status, inflammatory and antioxidant responses, grazing behavior, response to vaccination, and growth of beef calves. Experiment 1 used 86 Nellore calves (40 females and 46 males; body weight [BW] = 198 ± 30.8 kg; 8 ± 1 mo of age) weaned (day 0) and assigned into one of two treatments: saline (0.9% NaCl) or ITM (60 mg of Zn/mL, 15 mg of Cu/mL, 5 mg of Se/mL, and 10 mg of Mn/mL). Saline and ITM were administered subcutaneously at a dose of 1 mL/45 kg of BW. On day 0, calves were vaccinated against infectious bovine rhinotracheitis (IBR), parainfluenza-3 (PI₃), bovine viral diarrhea virus types 1 and 2 (BVDV-1 and 2) and bovine respiratory syncytial virus (BRSV). Blood samples and BW were collected on days 0, 3, 8, 15, 51, and 100, and grazing behavior was evaluated on days 1, 2, 4, 5, 6, 7, and 9. The ITM did not affect (P ≥ 0.56) serum mineral concentrations of Zn and Cu, but decreased (P ≤ 0.02) plasma concentrations of cortisol on days 3 and 8 and haptoglobin on day 3. The ITM increased (P < 0.01) plasma concentration of superoxide dismutase on days 8, 15, and 51 and tended to decrease (P = 0.08) plasma concentration of glutathione peroxidase on day 3. Furthermore, there were no effects of treatment (P ≥ 0.14) on most of the behavior variables evaluated, ITM reduced (P = 0.01) the seeking time on days 0 and 4. Furthermore, ITM tended to increase (P = 0.10) the serum titer concentration against IBR on days 15 and 51 but did not affect (P ≥ 0.12) titer concentration against PI₃, BVDV-1, and 2, and growth. Experiment 2 used 50 Brangus male calves (BW = 264 ± 34.1 kg; 8 ± 1 mo of age) weaned on day 0, vaccinated against respiratory diseases, stratified by BW, and randomly assigned to saline or ITM as described in experiment 1. Liver samples were collected on days 0, 14, and 197, blood samples on days 0, 14, and BW on days 0, 14, 44, 78, 122, 162, and 197. The ITM increased (P ≤ 0.03) the liver concentration of Cu and Se on day 14 but did not affect (P ≥ 0.17) the liver concentration of Zn and Mn. In addition, ITM increased (P = 0.05) the serum titer concentration against BVDV-2 but did not affect (P ≥ 0.20) the titer concentrations against IBR, PI₃, BVDV-1, and BRSV, and did not affect (P ≥ 0.29) the growth. In conclusion, ITM application at weaning improved Cu and Se status, enhanced antioxidant and immune responses, and reduced stress and inflammation in calves, though it did not affect growth.