A 2 year follow-up of effects of biotechniques on reproduction in the domestic rabbit, Oryctolagus cuniculus.

Routinely employed reproductive techniques such as gonadotropin treatment (0.3 mg follicle-stimulating hormone (FSH) subcutaneously twice daily for three consecutive days) followed by natural mating or artificial insemination as well as induction of ovulation by human chorionic gonadotropin (hCG) (75 i.u. hCG intravenously) were analysed in the rabbit after 2 years of consecutive experiments. 85% of gonadotropin-treated animals mated spontaneously. All 222 FSH-primed donor rabbits and 59 hCG-injected non-primed controls ovulated. The average number of ovulations per female was 30 (FSH and hCG) and 7.4 (hCG only). The fertilization rate was 88%, and 22.7 embryos were recovered per FSH-treated donor rabbit. With increasing time after mating the embryo recovery rate decreased (day 1 post coitum (p.c.), 36 embryos per rabbit; day 3 p.c., 26 embryos per rabbit; day 5 p.c., 16 embryos per rabbit) and a higher percentage of females had no embryos recovered. Embryo recovery was poor in donors with ovulation numbers greater than 40. Artificial insemination of nonreceptive females yielded smaller numbers of embryos compared with natural mating. Differences in fertility between the seasons of the year was revealed to be small. We conclude that gonadotropin treatment is efficient in increasing the number of embryos. Management of laboratory rabbits (dating, mating and expected number of embryos) is more predictable, and experiments can be performed successfully in all seasons of the year. However, the incidence of embryonic mortality seems to be increased when gonadotropin treatment is applied.