Some aspects of equine embryo transfer

Area of Science:

• Reproductive biology
• Veterinary science
• Embryology

Background:

• Embryo recovery and transfer are crucial in equine assisted reproduction.
• Understanding factors affecting success rates in mares, particularly those with prior breeding issues (barren mares), is important.

Purpose of the Study:

• To evaluate embryo recovery success rates in experimental versus barren mares.
• To assess the impact of in vitro embryo maintenance duration on pregnancy rates.
• To determine pregnancy maintenance rates at different time points after ovulation.

Main Methods:

• Comparing embryo recovery success rates between experimental and barren mares.
• Assessing twin embryo incidence post-recovery.
• Evaluating pregnancy rates following non-surgical embryo transfer after short (<3 h) versus long (>6 h) in vitro maintenance.
• Monitoring pregnancy rates in recipients at 24, 30, and 100 days post-ovulation.

Main Results:

• Successful embryo recovery rates were 56.0% in experimental mares and 34.3% in barren mares.
• Twin embryo incidence was 10.7% in experimental mares and 16.7% in barren mares.
• In vitro maintenance of embryos for >6 h significantly reduced pregnancy rates compared to <3 h.
• Pregnancy rates at 100 days were significantly lower than at 24 and 30 days (P < 0.05).

Conclusions:

• Barren mares exhibit lower embryo recovery success rates compared to mares with no prior breeding problems.
• Extended in vitro embryo culture negatively impacts pregnancy establishment and maintenance in equine recipients.
• Pregnancy loss occurs between 30 and 100 days post-ovulation, highlighting the need for further investigation into late-term pregnancy maintenance.