Successful non-surgical transfer of horse embryos to mule recipients.

This research explores the successful transfer of horse embryos into mule recipients without the need for surgical procedures. It shows that the two mules who were cycling was able to deliver healthy foals.

Objective and Methodology

• The main goal of the research was to investigate the capability of mules – hybrid animals produced by mating a horse mare and a Jack donkey, known for their general infertility – to carry horse embryos and result in a successful birth.
• Five horse embryos were non-surgically transferred to three mules – two cyclic and one acyclic.
• The mares and cycling mules had oestrus and ovulation induced by d-cloprostenol and human chorionic gonadotrophin (hCG) respectively.
• The acyclic mule received oestradiol benzoate when the embryo donor was showing oestrus and progesterone after the donor ovulated until pregnancy was confirmed.
• The embryos were collected non-surgically on the seventh day after ovulation, and then transferred transcervically into the uteri of the mules.

Results

• For the mules that became pregnant, blood samples were checked for equine chorion gonadotrophin (eCG), progestagen, and total conjugated oestrogen concentrations until around six months of gestation.
• None of the embryos transferred to the acyclic mule resulted in successful pregnancies, while both embryos transferred to the cycling mules led to the birth of live foals.
• There were notable differences in concentrations and duration of eCG secretion between the two pregnant mules, yet both animals developed secondary corpora lutea beyond day 40 of gestation, similar to a normal intraspecies horse pregnancy.
• Also, the rise in serum estrogen concentrations from around day 90 resembled that seen in normal pregnant mares.
• Both mules delivered spontaneously on day 348 of gestation, and the resulting colt foals developed normally until weaning.

Conclusions

• The research outcomes illustrate that cycling mules have the ability to carry a horse conceptus after non-surgical embryo transfer and give birth to a normal mature foal.
• This advancement sheds light on the potential application of non-surgical embryo transfer in mules and possibly other equine animals, opening up new methods for increasing populations and preserving genetic diversity.