Effects of a single trace mineral injection on body parameters, ovarian structures, pregnancy rate and components of the innate immune system of grazing Nellore cows synchronized to a fixed-time AI protocol
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2019 Elsevier B.V. Two experiments evaluated the effects of injectable trace minerals (ITM) administered 30 d before artificial insemination (AI) on body weight (BW), body condition score (BCS), ovarian structures, pregnancy rate, and components of the innate immune system of grazing Nellore cows. In Exp. 1, 20 multiparous cows (BCS = 4.3 0.4, scale 1 to 9; BW = 388 35 kg) were kept on marandu-grass pasture (Urochloa sp.) and offered free-choice access to a trace mineral supplement. Cows were stratified by BCS and BW and randomly assigned to 1 of 2 treatments: subcutaneous injection (6 mL/cow) of saline solution (0.9% NaCl) or ITM (Multimin 90; containing 60, 10, 5, and 15 mg/mL of Zn, Mn, Se and Cu, respectively) administered 30 d (d -30) before AI (d 0). Pregnancy diagnosis was evaluated on d 30, BW and BCS on d -30, 0 and 30, ovarian structures on d 0 and 14, and blood samples collected on d -30, -26, -22, -17, -11, 0, 7, 14, 21 and 30 for analysis of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), haptoglobin, ceruloplasmin and progesterone (P4). In Exp. 2, 573 multiparous cows (BCS = 4.8 0.5; BW = 400 35 kg) received free-choice access to a trace mineral supplement and were assigned randomly to 1 of 2 treatments (ITM or saline injection 30 d before AI). In Exp. 1, ITM did not affect (P 0.12) BW, BCS, corpus luteum (CL) diameter and volume, pregnancy rate, and plasma concentrations of haptoglobin, ceruloplasmin and P4 compared to saline injection. Administration of ITM increased (P 0.008) plasma concentrations of SOD on d -22 and -17 and GSH-Px on d -26 compared to saline. In Exp. 2, ITM tended to increase the pregnancy rate compared to saline injection for cows with BCS < 5 (P = 0.09; 58.4 vs. 46.8 6.5% respectively), but not for cows with BCS > 5 (P = 0.36; 71.8 vs. 67.6 3.5% respectively). Therefore, a single ITM injection 30 d before AI did not alter the body parameters, ovarian structures and acute phase response of grazing Nellore cows, but increased plasma concentrations of antioxidant enzymes, and tended to improve pregnancy rates to AI in cows with BCS < 5.
