Successful transfer of the embryos of Przewalski’s horses (Equus przewalskii) and Grant’s zebra (E. burchelli) to domestic mares (E. caballus).

The study involves the successful transfer of embryos from Przewalski’s horses and Grant’s zebra into domestic mares, indicating that such extra-specific embryo transfers could be a useful aid in breeding exotic horse species in captivity.

Methodology

• The researchers collected blastocysts non-surgically from animals of two species, Przewalski’s horse and Grant’s zebra.
• These blastocysts were then transferred extra-specifically—meaning that they were transferred to surrogate mothers of different species—to domestic horses and donkeys.
• Additionally, the researchers also surgically transferred nine Przewalski’s horse embryos to domestic Welsh-type pony mares, and twelve Grant’s zebra embryos to various pony and domestic donkey recipients.
• Non-surgical transfers were also performed for two Przewalski horse embryos and one Grant’s zebra embryo.

Findings

• The researchers’ efforts resulted in seven successful pregnancies from the surgical transfer of Przewalski’s horse embryos, with four of these pregnancies eventually resulting in live foals.
• Three successful pregnancies were established when zebra-embryos were surgically transferred to horses, with two of these pregnancies going to term.
• However, the attempt to transfer zebra embryos to donkeys was relatively unsuccessful, with only two pregnancies established and neither of them going to term.
• Furthermore, no pregnancies resulted from the non-surgical transfers.
• The researchers also made observations about the maternal immunological response to the extra-specific embryo, noting that it was pronounced but did not correlate with the success or failure of the pregnancy.

Implications

• The study shows that extra-specific embryo transfer—an approach typically used for breeding exotic horse species in captivity—can be successful.
• This breakthrough could have significant implications for animal conservation, particularly for endangered or threatened species of equids (a group that includes horses, donkeys, and zebras).
• However, the varying rates of success depending on the combination of donor and recipient species hint at potential complexities and challenges involved in the process.