In vitro fertilization and embryo transfer of rabbit oocytes collected at different times after P-LH injection.

No difficulties were encountered in the collection of preovulatory oocytes from the follicles of rabbits. A mean of 11.7 ova were recovered by follicle puncture. In vitro fertilization of the preovulatory oocytes was influenced by their stage of maturation. The highest fertilization rate (83%) was obtained using oocytes collected 9 h after injection of P-LH shortly before ovulation. Only after pretreatment with FSH-P was it possible to fertilize some preovulatory oocytes without administration of P-LH. In vitro fertilized preovulatory oocytes developed in culture. After 4-5 days 47-64% reached the blastocyst stage; the corresponding rate for in vivo fertilized oocytes was 48%. After transfer of in vitro fertilized preovulatory oocytes 19-28% implantations were achieved.