Effects of parenteral supplementation of Cu in female cattle with different levels of cupremia
The experiment was carried out in two stages with the objective of determining the effect of parenteral supplementation of 50 mg Cu on the reproductive behaviour of both hypo- and normocupremic cyclic female cattle. In the first stage, 62 hypocupremic, cyclic animals were selected, 32 heifers (16 in the control group and 16 in the treatment group) and 30 cows (12 in the control group and 18 in the treatment group). In the second stage, 98 normocupremic, cyclic heifers were selected (49 in the control group and 49 in the treatment group). 50 mg of Cu were administered to the animals in the treatment groups parenterally (subcutaneously) every two months until three successive applications were completed, while the control animals were not given copper supplementation. The effects of the copper therapy on cupremia and the percentage of heat and gestations presented were determined. The relative risk of treated animals of presentating anoestrus and service repetition was evaluated by the formation of a 2 × 2 contingency table and the application of a χ² test. The levels of serum copper were compared using a t-test, while heat and gestations were compared using a proportion comparism test. The parenteral administration of 50 mg Cu in hypocupremic, cyclic heifers and cows led to significant increases of cupremia ( P<0.001) and the percentages of heat presentations and gestations ( P<0.01); in the normocupremic animals, there were significant increases in the values of serum copper ( P<0.0001), heat presentations ( P<0.01) and gestations ( P<0.001), especially in animals with cupremia values below 14 mmol/L. The treatment reduced the relative risk of reproductive disorders. It is concluded that the parenteral administration of 50 mg Cu in female cattle with Cu blood serum level <14 mmol/L increased cupremia and the percentages of heat presentations and gestations, and reduced the relative risk of reproductive disorders.