143 TREATMENT WITH VITAMINS A AND E IMPROVE OOCYTE QUALITY AND IN VITRO EMBRYO DEVELOPMENT IN BOS INDICUS COWS

Abstract

We assessed the impact of a single intra-muscular injection of vitamins A and E on oocyte quality and yield and early embryo development in Bos indicus cows. Twenty Bos indicus cows, of Gyr, Brahman, and Nellore breeds, weighing between 450 and 600 kg were subjected to ovum pick-up (OPU). Oocytes were collected in Dulbecco’s PBS (DBPS) containing heparin and antibiotics, counted, and morphologically classified. Viable oocytes were taken to the laboratory, in vitro matured for 24 h and in vitro fertilized using 25 million sperm mL^–1. After 168 h of incubation (39°C, 5% CO₂), viable embryos were counted and classified. Then, after 10 days, the cows received an intra-muscular injection of 1 000 000 UI of vitamin A and 1 g of vitamin E, and, after 12 days, were again subjected to the same procedure described above. Differences in oocyte yield and embryo development were analysed using paired t-test. The 40 OPUs from 20 cows yielded a total of 520 oocytes. Nellore and Brahman cows produced more embryos/cow (P < 0.01) compared with Gyr. After vitamin treatment, the cows produced more oocytes (n = 303; P < 0.01) compared with the previous OPU (n = 217), resulting in 95 more viable oocytes (31%). Brahman, Gyr, and Nellore cows yielded 11.2 ± 1.8, 8.5 ± 1.5, and 12.0 ± 2.6 oocytes before vitamin treatment, respectively. From those oocytes, 224 embryos were obtained, 89 before vitamin injection and 135 after treatment (P < 0.02), with 36 more embryos (40%) produced. Irrespective of breed, cows responded equally to vitamin injection. A single parenteral injection of vitamins A and E had a significant positive effect on oocyte yield after OPU and in vitro embryo development on Bos indicus cows. We suggest that this effect is probably due to the positive influence of retinoids on oocyte and embryo development.