The use of early pregnant mares as embryo recipients.

The research investigates the use of early pregnant mares as embryo recipients. The goal of the study is to understand if a mare can carry both its own embryo and a transferred one simultaneously and evaluate whether the mare’s current pregnancy status influences the conception rate.

Study Design

• The research team worked with 14 traditional, cyclic mares. These mares underwent treatment to synchronize their oestrus, or fertility periods, and ovulation.
• The mares were artificially inseminated using fresh semen. Upon ovulation, the mares were categorized into either a donor or a receiver group.
• The objective was to achieve a synchrony level of more than or equal to 2 days.

Embryo Transfer Process

• The team collected ten embryos on either Day 6 or 7 after the mares’ ovulation (considered Day 0).
• The embryos were nonoperatively transferred into two types of recipient mares: inseminated recipient mares (IRM) that had ovulated five days after the donor, and pregnant recipient mares (PRM) that ovulated two to seven days before the donors.
• Using ultrasound examination, the size and development of embryos from both the recipient mare (RE) and donor mare (TE) were examined and differentiated.

Results of the Experiment

• If twin pregnancy occurred, the RE was gently crushed during days 14-16.
• They induced abortion in all mares on Day 30.
• Out of 6 TE, 3 developed in IRM. Out of these, 2 had developed twin pregnancy, whereas 4 had developed singleton pregnancy.
• All four of the TE didn’t develop in PRM that were between 9-14 days, and one of these PRMs even lost her own embryo following the ET.

Conclusion

• Based on the findings, the study concluded that a mare could maintain her own embryo and a transferred embryo simultaneously. However, it was also noted that a mare’s pregnancy status does not enhance the conception rate if the mare ovulates before the donor.