Studies On In Vitro Maturation, In Vitro Fertilization And Cryopreservation Protocols Of Goat Follicular Oocytes

The present study was conducted to investigate the effects of size and cryopreservation protocols of follicular oocytes on in vitro maturation and in vitro fertilization in goat. The main results showed as follows:1. The IVM rates of goat oocytes derived from follicles with size of larger than 5mm, 3~4.9mm and 2~2.9mm in diameter were 76.85%, 72.04% and 62.26%, respectively. 24h after the matured oocytes were inseminated in vitro, the 2-cell cleavage rates were 10.74%, 9.80% and 6.47%, respectively. The IVM rates and IVF rates of oocytes derived from follicles with size of larger than 3mm in diameter were significantly higher than those derived from follicles with size of 2-2.9mm in diameter (P<0.05).2. There was no significant difference in the rates of morphologically normal thawed oocytes frozen at different developmental stages (IVCOh, IVC8h, IVC16h and IVC24h) and derived from follicles in different size. The IVM rates of thawed oocytes derived from follicles with size of larger than 3mm in diameter were 18.41%~22.07%, and they were significantly higher than those derived from follicles with size of 2~2.9mm (10.13%~13.55%) (P<0.05). Only the oocytes frozen at IVM stage could be inseminated and cleaved in the study. The 2-cell cleavage rates of oocytes derived from follicles with size of larger than 5mm and 3-4.9mm were 6.38% and 5.46%, respectively, and they were significantly higher than those derived from follicles with size of2~2.9mm (P<0.05).3. In GV oocytes which were derived from follicles with size of larger than 3 mm, the rate of morphologically normal thawed oocytes frozen with EG and by OPS straw (EG-OPS) was 75.10%. It was significantly higher than those frozen with EG-GMP (49.31%) and Glycerol-OPS (58.75%) (P<0.05), The rate of morphologically normal thawed oocytes frozen with Glycerol-GMP was significantly lower than other groups (P<0.05). The IVM rate of oocytes frozen with EG-OPS was 18.84% and it was significantly higher than those frozen with EG-GMP, Glycerol-OPS and Glycerol-GMP (P<0.05). None of IVM oocytes could be inseminated and cleaved from four groups.4. In IVM oocytes which were derived from follicles with size of larger than 3 mm, the rates of morphologically normal thawed oocytes frozen with EG-OPS and EG-GMP were 77.95% and 68.54%. There was no significant difference between them (P>0.05), but they were significantly higher than those frozen with glycerol (58.14%, 47.69%) (PO.05). The cleavage rate of thawed oocytes frozen with EG-OPS was significantly higher than those frozen with Glycerol-OPS (P<0.05).5. The rates of morphologically normal thawed oocytes exposed to equilibration solution for 10 min and 15 min were 73.70% and 74.10%, respectively. There was no significant difference between them, but they were significantly higher than those for 25 min (P<0.05). After IVF, the cleavage rates of these oocytes were 4.67%, 4.92% and 1.45%, respectively. The former two groups were significantly higher than the latter (P<0.05).6. The ovarian tissues were vitrified with three different cryoprotectants. The rates of morphologically normal thawed oocytes recovered from these tissues were 65.32%, 63.01% and 59.69%, respectively. The IVM rates were 11.79%(Group I ), 6.27%(Group II) and 6.30%(GroupIII), and the group I was significantly higher than group II and group III (P<0.05). The ovarian tissues could be effectively vitrified with cryoprotectant I .