Measurement of early pregnancy factor activity for monitoring the viability of the equine embryo.

This research article investigates the usage of measuring early pregnancy factor (EPF) activity as a way to monitor the viability of equine embryos, primarily in horses. The findings suggest that equine EPF can be detected in the serum of pregnant mares as early as two days after ovulation, making this method useful for monitoring embryo viability and early detection of embryonic death.

Monitoring Viability of Embryos

• The study started by monitoring the viability of embryos in two scenarios: before they were removed from donor mares and after they were transferred to recipient mares.
• Such evaluation was performed through the detection of early pregnancy factor (EPF) using the rosette inhibition test (RIT). EPF is a protein that is produced in the earliest stage of pregnancy and hence its detection indicates pregnancy.

EPF Detection Process

• The EPF activity was measured in various stages for the donor mares: prior and after natural mating at natural estrus; post-ovulation on Days 2, 5 and 8; and after embryo extraction (Day 8) on Days 8, 9, 10 and 13.
• These retrieved embryos were immediately moved to recipient mares and the EPF activity in these mares were noted on the day of transfer and the following days.
• Afterwards, pregnancy was validated around Day 12 to 14 using ultrasound.

EPF Detection Outcomes

• It was observed that EPF activity increased to the pregnant level in the donor mares just 2 days post-ovulation.
• Interestingly, two days post embryo extraction, EPF activity went back to the non-pregnant level in these donor mares.
• Comparatively, among the 7 recipient mares, 3 were confirmed pregnant after 12 days of embryo transfer as per the ultrasound, spotting increased EPF activity equivalent to the minimum level observed in pregnant mares.
• On the other hand, the remaining recipient mares, who weren’t pregnant post embryo transfer, showed high EPF activity only for 2 to 3 days before plummeting to non-pregnant level.

Study Conclusion and Applications

• Based on these observations, the study concluded that EPF can be detected in pregnant mares as earlier as Day 2 post-ovulation. This suggests that EPF activity can be used to evaluate in vivo viability of equine embryos as well as early detection of embryonic death.
• The usage of EPF activity proves as a quick and feasible solution to assess the successful progress of embryonic transfer and subsequent pregnancy in mares.