Effect of injectable trace mineral at weaning on growth and physiology of Nellore calves under feed restriction.

Calves are susceptible to a wide variety of stressors besides the seasoning low forage availability during their weaning phase. Thus, it is ideal if they receive adequate trace mineral supplementation during this period. This study evaluated the effect of injectable trace minerals (ITM) on performance, concentration of oxidative stress enzymes, and biochemical plasmatic parameters in Nellore calves during the weaning phase and under feed restriction. A total of 30 Nellore calves were used at the age of 7 ± 1 month and 176.23 ± 21.68 kg of initial body weight (BW). These animals were allocated in Urochloa decumbens pasture for 28 days and transferred to Urochloa brizantha cv Marandu pasture for another 28 days. The treatments were: Saline (saline solution; 0.9% NaCl) and ITM (Multimin®, providing: 15 mg Cu/mL, 60 mg Zn/mL, 10 mg Mn/mL, and 5 mg Se/mL). Both treatments were applied subcutaneously in the ratio of 1 mL/45 kg of BW. At the end of the experiment (d 56), animals were lighter than on d 0 in both treatments (P < 0.05). However, calves that received the ITM treatment presented lower body weight (P < 0.05) on d 56, compared to those in the control group. No significant difference (P > 0.05) was observed on the concentrations of oxidative stress enzymes. Moreover, no significant difference (P > 0.05) was observed in the plasmatic parameters; these were at normal range or slightly below the concentrations described for the species. We concluded that, in a feed restriction condition, the use of ITM in weaned calves did not improve performance, and the concentration of oxidative stress enzymes, and biochemistry variables. Therefore, we do not recommend using injectable trace minerals in the concentrations used in this study in animals under such stressful conditions.