Comparison of Oocyte Collection Yield Between Conventional Follicle Scraping and Ultrasound-Guided Follicle Aspiration in Postmortem Excised Horse Ovaries.

Overview

• This study compared two techniques for collecting oocytes from horse ovaries after death to determine which yields more oocytes for cloning and genetic preservation.
• The ultrasound-guided follicular aspiration (OPU) technique was found to be more efficient than the conventional follicle scraping method in retrieving oocytes.

Background and Purpose

• Post-mortem oocyte collection is important to preserve genetic material from valuable mares and to obtain recipient oocytes for cloning.
• The efficiency of oocyte retrieval directly influences the chances of producing viable embryos.
• The study aimed to evaluate and compare two oocyte retrieval methods from excised horse ovaries:
• Conventional follicle scraping (Scraping)
• Ultrasound-guided follicle aspiration (OPU)

Methods

• Total of 22 replicates conducted, split evenly: 11 for Scraping and 11 for OPU.
• A total of 50 ovaries were processed: 28 with the Scraping method and 22 with OPU.
• Parameters measured included:
• Number of follicles aspirated per ovary
• Oocyte recovery rate (ORR): percentage of follicles yielding oocytes
• Number of oocytes obtained per ovary
• Processing time per oocyte
• Oocyte searching time
• Volume of medium used in processing
• For consistency, the same operator searched for oocytes and was blinded to the method used.

Results

• Number of follicles aspirated per ovary:
• OPU: 13.6 ± 3.8 follicles
• Scraping: 9.5 ± 3.5 follicles
• Oocytes recovered per ovary:
• OPU: 9.1 ± 3.0 oocytes
• Scraping: 4.7 ± 2.1 oocytes
• Processing time per oocyte:
• OPU: 1.8 ± 0.8 minutes
• Scraping: 4.1 ± 1.6 minutes
• Oocyte Recovery Rate (ORR):
• OPU: 66.7%
• Scraping: 50%
• Volume of medium used:
• No significant difference between methods (19.6 ± 10.4 mL OPU vs. 21.6 ± 11.0 mL Scraping)
• Oocyte condition:
• OPU resulted in a higher proportion of denuded oocytes (37.5%) compared to Scraping (18.6%)

Interpretation and Implications

• The ultrasound-guided follicular aspiration method is superior in several key aspects:
• It accesses and aspirates more follicles per ovary.
• It recovers a greater total number of oocytes per ovary.
• It is more time-efficient, requiring less time per oocyte processed.
• It has a higher oocyte recovery rate, increasing the efficiency of genetic material collection.
• Despite these advantages, the OPU method produces a higher percentage of denuded oocytes, which may influence downstream applications such as fertilization or cloning protocols.
• Volume of processing medium and operator blinding ensures a fair comparison without bias due to processing differences.
• These findings support adopting the ultrasound-guided aspiration technique over scraping to maximize oocyte yields from post-mortem horse ovaries, potentially improving cloning success and genetic preservation efforts.

Conclusion

• Ultrasound-guided follicular aspiration is a more efficient method than conventional follicle scraping for collecting oocytes from post-mortem excised horse ovaries.
• This technique improves the number of harvested oocytes and reduces processing time, which is valuable for research and clinical applications involving horse oocyte preservation and cloning.