Factors influencing oocyte recovery during ultrasound-guided follicle aspiration in mares: A postmortem study.

This research examined how different variables during an ovum pick-up (OPU) procedure in horses, such as vacuum and injection pressures, needle twisting, the number of follicle flushes, and the type of flushing media, affect the oocyte recovery rate and morphology. It found that the highest oocyte recovery was achieved by scraping the follicle with the needle and flushing the follicle up to ten times, while high injection pressures resulted in more oocytes being lost in leaked fluid.

Study Design and Methodology

• The researchers studied 120 post-mortem excised ovaries from mares, performing a procedure that mimicked an ovum pick-up (OPU) operation that would be carried out on a living mare. In total, 1336 follicles were punctured and aspirated.
• The researchers manipulated several variables: the aspiration pressure, the injection pressure used to flush follicles, the number of times each follicle was flushed, and the type of flushing media used. Quantities were varied in a controlled manner to observe the effects on the oocyte recovery rate (ORR), a measure of the number of viable eggs retrieved.

Findings and Conclusions

• Aspiration pressure did not significantly affect the ORR. However, high pressure resulted in more denuded (naked or stripped) oocytes than low pressure.
• A high injection pressure for flushing follicles was associated with a lower ORR and more oocytes lost in the leaked fluid.
• The number of flushes per follicle significantly influenced the ORR. The ORR was maximized when the follicle was flushed ten times.
• More oocytes were lost outside the ovary in leaked fluid when the number of flushes was three or more.
• Scraping the follicle wall by twisting the needle resulted in a better ORR than not scraping.
• The type of flushing media used did not significantly impact the ORR.
• The study concluded that the best results in oocyte recovery are achieved when scraping the follicle with the needle and flushing it ten times.

Implications

• The results provide valuable insight into optimizing OPU in horses. This information could lead to better fertility treatments and breeding practices, improving the efficiency and success rates of these procedures.
• However, the findings must be confirmed with further research before changes in practice can be fully endorsed. This study was conducted on post-mortem ovaries, so real-world factors in live mares might yield different results.