Effect of age of equine embryos and method of transfer on pregnancy rate.

The study explores how the age of a horse embryo (seven or eight days post-ovulation) and the method of transfer (surgical vs. non-surgical) impact pregnancy rates.

Methods and Experiment Design

• The experiment was a 2 X 2 cross-classified design – a statistical model commonly used in experimental designs, to study the effect of embryo age (seven days vs eight days post-ovulation) and the method of embryo transfer (surgical vs non-surgical) on pregnancy rates at 50 days of gestation.
• Embryos were recovered using a Foley catheter and an isotonic saline solution (Dulbecco’s phosphate-buffered saline or PBS), on either day seven or day eight post-ovulation.
• Identified embryos were placed in millipore-filtered PBS containing 20% heat-inactivated steer serum and kept at room temperature until transferred.
• Embryos were randomly chosen to be transferred either surgically via a flank incision or nonsurgically using a sterile insemination pipette.
• The surgical method placed the embryo in the uterine horn ipsilateral to the corpus luteum, while the non-surgical method deposited the embryo into the uterine body.

Findings

• The recovery rates of embryos collected on days seven (75.5%) and eight (81.9%) were similar and statistically insignificant (P > .05), indicating embryo age did not affect recovery rate.
• Pregnancy rates were also insignificant between mares receiving seven-day old embryos (60%) or eight-day old embryos (57%), meaning the embryo’s age didn’t significantly influence pregnancy success.
• However, surgical transfer of embryos resulted in significantly more pregnancies (72%) than non-surgical transfers (45%), making this method comparatively more effective.
• Further, the transfer of eight-day old embryos surgically resulted in more pregnancies (75%) compared to non-surgically (40%).
• Within the method of transfer, the difference in pregnancy rates for surgical transfer of seven-day and eight-day embryos was statistically insignificant (69% and 75% respectively).
• However, there was a trend towards higher pregnancy rates for non-surgical transfers with seven-day embryos (50%) compared with those of eight-day embryos (40%), though the difference wasn’t statistically significant.

Conclusion

• In conclusion, the study found that pregnancy rates didn’t significantly vary with the age of the embryo (seven or eight days post-ovulation). But, method of transfer significantly impacts the pregnancy rate with surgical transfer being more effective than non-surgical counterpart.