Impacts of the injections of vitamins C and E on reproductive events in Holstein dairy cattle during a synchronized estrus

Abstract

High milk production and stressing environmental factors as heat stress, reduce reproductive performance in dairy cattle and decrease blood concentrations of vitamins C and E, which are necessary to sustain fertility in mammals. The objective of this thesis was to develop a reproductive strategy to improve pregnancy rate in Holstein dairy cows after a synchronized estrus by supplementing vitamins C and E. To accomplish this objective, Holstein dairy cows were assigned to one of two groups: 1, Control (n=80) cows were not injected with vitamins. 2, vitamins C and E (n=125), the cows were injected with vitamin C (3,000-6,000 mg) and E (3,000-6000 IU) before and after a synchronized estrus during four experiments (I-IV). The impacts of vitamins injections on reproductive performance in dairy cattle were measured on size of the preovulatory follicle and corpus luteum, blood concentrations of estradiol and progesterone, as well as pregnancy rate at 30-45 days after artificial insemination. In general, the supplementation with vitamins did not affect (p˃0.05) size of preovulatory follicle or corpus luteum. Similarly, blood concentrations of estradiol and progesterone were not affected (p˃0.05) by vitamins supplementation. Regarding pregnancy rate, more cows were found pregnant after artificial insemination in the group injected with vitamins than those in control group. However, significant differences were not obtained between groups in any of the experiments (p˃0.05), but a tendency was found in experiment II (p=0.06). In conclusion, injections of vitamins C and E before and after a synchronized estrus did not affect preovulatory follicle and corpus luteum development, blood concentrations of estradiol and progesterone, but tend to improve pregnancy rate in dairy cattle.