Fertilization in vitro of oocytes matured in vivo in the blue fox (Alopex lagopus).

Six unmated blue fox vixens were killed 2-3 days after peak vaginal electrical resistance. Measurements of luteinizing hormone (LH) showed that this corresponded to a time period of 6-10 days after the preovulatory LH peak in these vixens. A total of 63 ova were collected from the oviducts of the vixens, and 45 of the ova were used for study of fertilization in vitro. The ova were placed in 50 microliter droplets of fertilization medium and inseminated with 15,000-45,000 frozen-thawed silver fox spermatozoa that had been separated by swim-up technique, except for nine ova that served as controls for parthenogenesis. Only two of the 36 inseminated ova, both from a vixen killed 6 days after the preovulatory LH peak and inseminated with 15,000 spermatozoa, developed past the four-cell stage. One reached the morula stage 144 h after insemination. Despite a low success rate, the present experiment shows that fox ova matured in vivo may be fertilized and undergo initial embryonic development in vitro.