Comparative Evaluation of Follicular Flushing Frequency and Scraping Time During Ovum Pick-Up in Mares: Effects on Oocyte Recovery Rate and Technical Considerations.

Transvaginal ultrasound-guided follicular aspiration or ovum pick-up (OPU) has become the standard technique for oocyte collection in mares for intracytoplasmic sperm injection (ICSI). Although repeated follicular flushes and wall scraping are commonly used to improve oocyte recovery rate (ORR), the relative contribution of each remains unclear. This study aimed to compare the effects of multiple flushes versus controlled scraping time on ORR in mares. A controlled trial was conducted in two phases: (1) an ex vivo phase using slaughterhouse ovaries (n = 32), and (2) an in vivo phase in clinically healthy mares (n = 9). Follicles were assigned to two groups: multiple flushes (MF, 10 flushes with intermittent scraping, lasting 18 s in total) or single flush (SF, 18 s of continuous scraping followed by 1 flush). A total of 489 follicles were aspirated ex vivo and 143 in vivo. Results showed no significant difference in ORR between MF and SF groups in either phase (ex vivo: 63.8% vs. 59.5%; in vivo: 48.3% vs. 44.3%; p > 0.05). However, MF used significantly more flushing medium per follicle in the ex vivo model (p < 0.05). No significant differences were found in aspiration time or incidence of clots and blockages in the aspiration lines. A significant correlation was observed between clot number and aspiration system blockage (r = 0.497, p = 0.036). Continuous scraping without repeated flushing reduces medium usage but may increase operator fatigue and the risk of clot formation and system obstructions. Therefore, optimising scraping duration could improve the efficiency of oocyte recovery procedures while simplifying the technique and reducing costs. Further research is required to refine scraping protocols, reduce operator fatigue, and prevent complications related to clot formation.