Establishment and maintenance of donkey-in-mule pregnancy after embryo transfer in a non-cycling mule treated with oestradiol benzoate and long-acting progesterone

Abstract

Female mules are considered as infertile; however, they could be used as recipients in interspecific embryo transfer. This study reports for the first time how it is possible to obtain the birth of a live Andalusian donkey foal after transfer a donkey embryo to a non-cycling mule. Two non-cycling mules were used as recipients, oestradiol benzoate was administered when donors showed oestrus and long-acting progesterone after ovulation. The mules also received long-acting progesterone every 7 days until 120 days of gestation. One embryo was collected from the two donor jennies and transferred to one of the mules after 5 days of progesterone treatment. Pregnancy was established and maintained after embryo transfer. The pregnant mule carried to term and delivered a live donkey foal after 375 days of pregnancy. In conclusion, non-cycling mules treated with oestradiol benzoate and long-acting progesterone can be successfully used as recipients of donkey embryos, which open new ways for the conservation of endangered donkey species.