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

Post-mortem oocyte collection serves to preserve the genetic material of valuable mares and to obtain recipient oocytes for cloning purposes. Therefore, the number of oocytes retrieved per ovary is a critical factor in increasing the likelihood of obtaining a viable embryo. This study evaluated the efficiency of two post-mortem oocyte retrieval techniques: follicular scraping (Scraping) and ultrasound-guided follicular aspiration (OPU). The comparison was based on several parameters, including the number of follicles aspirated per ovary, oocyte recovery rate (ORR), number of oocytes obtained per ovary, processing time, oocyte searching time, and the volume of medium used. A total of 22 replicates were performed (11 for each group), processing 28 ovaries in the Scraping group and 22 ovaries in the OPU group. Oocytes were searched by the same operator, who was blinded to the treatment group. The results demonstrated that the OPU technique was significantly more efficient than Scraping in most evaluated parameters: number of follicles aspirated per ovary (13.6 ± 3.8 vs. 9.5 ± 3.5), oocytes recovered per ovary (9.1 ± 3.0 vs. 4.7 ± 2.1), processing time per oocyte (1.8 ± 0.8 min vs. 4.1 ± 1.6 min), and ORR (66.7% vs. 50%) (p < 0.05). No significant difference was found in the volume of medium used (19.6 ± 10.4 vs. 21.6 ± 11.0 mL). However, the OPU technique resulted in more denuded oocytes (37.5%) than the Scraping technique (18.6%; p < 0.05). In conclusion, ultrasound-guided follicular aspiration yielded a higher number of oocytes per ovary compared to the standard scraping technique.