Assisted reproductive technologies in donkeys

Interest in the development of assisted reproductive technologies (ART) in donkeys is growing due to improved consciousness of the necessity to preserve biodiversity and of jennies milk properties. Induction of ovulation is a prerequisite to successfully apply artificial insemination (AI) and embryo transfer (ET). GnRH agonists are effective in this species, and we observed that a single s.c. administration of as low as 0.04 mg buserelin acetate can induce ovulation after 24–48 h in estrous jennies. In literature, pregnancy rates after AI with cryopreserved semen in jennies were low (0–20%). At our lab, an overall 36.8% (14/38) per cycle pregnancy rate was obtained with two timed frozen-thawed semen AIs, 16–18 and 36–38 h post-induction, with the best results (8/13) when seminal plasma was added post-thaw. With a single AI 24 h post-induction, however, pregnancy rate was 20% (2/10). A satisfactory embryo recovery rate, 76%, and a very low 14 days recipients pregnancy rate after transcervical ET, 22%, were reported by our group. However, it was later demonstrated that cervical stimulation was not followed by a significant PGF2a release and that donkey embryo quality was good, and it was possible to raise recipients pregnancy rate to 50%, in the range of what commonly observed in horse commercial ET. The transfer of 11 vitrified donkey embryos resulted in 4 pregnancies at 14 days and in the birth of the first two foals from cryopreserved embryos in this species. Although improvements are still warranted, ARTs are today available in donkey.