In vitro fertilization and embryo transfer of pre-ovulatory rabbit oocytes.

The objective of this study was to develop an effective and successful technique of in vitro fertilization in rabbits that could lead us to start treatment of infertile couples by using extracorporal fertilization. Pre-ovulatory oocytes were harvested from follicles of virgin does 9 h after induction of ovulation by hCG injection, and incubated with in vivo capacitated sperm for 5 h. An 82% in vitro fertilization rate was achieved. The fertilized ova were cultivated for an additional 20, 44 and 68 h, and until they reached the hatched blastocyst stage. Most of these embryos (439) were transferred to 42 pseudopregnant recipients, asynchronous in the sense that they had been given hCG injections 0, 6, 12, 18, 24, 36 and 42 h later than the rabbits from which the ova had been obtained. With this type of synchronicity implantation rates of 31, 78, 52, 33, 52, 33, 51 and 10% were achieved, respectively. One hundred and twenty-eight embryos were not transferred to recipients but cultured in Ham's F-10 medium supplemented with 20% FCS. 77% of these embryos reached the stage of hatched blastocyst. A total of 143 young were born after 28-32 days of gestation and all are fertile till the third generation. Our results were obtained in a consecutive series of experiments, and demonstrated that in vitro fertilization can be made to work quite well in the rabbit, which in the early stages of embryogenesis has sufficient similarity to the human to make it a useful model for those wishing to acquire techniques applicable to human fertilization in vitro and embryo transfer.