Chronology of maturational events in goat oocytes cultured in vitro

Follicular oocytes were retrieved from goat ovaries, collected from a local slaughter house. These oocytes were cultured in TCM-199 with 20% heat inactivated goat estrous serum for 6, 12, 18, 24, 30, 31, 32 and 36 h at 39 °C; 5% CO 2 in air and 95% humidity. A total of 1465 good cumulus-enclosed oocytes were matured and fixed at different time intervals to establish the chronology of meiotic events occurring in goat oocytes during in vitro maturation. Results revealed that at 0 h, 78.3% of oocytes were in the GV stage. A total of 57.4% of the oocytes were found in diakinesis stage at 6 h culture. Peak (51.1%) metaphase-I (M-I) was noted at 12 h. M-II was first observed after 18 h of culture, but at 32 h the maximum (71.6%) oocytes were in M-II stage. The percentage of oocytes reaching M-II was comparatively less at 30, 31 and 36 h (50.3, 55.8 and 59.7%), thus indicating that 32 h of culture is the most suitable time for goat oocyte maturation in vitro.