Efficacy of tuohy needle in oocytes collection from excised mare ovaries

Oocyte aspiration from equine follicles gives a low recovery rate and yields oocytes largely denuded of cumulus cells. Follicle scraping is labour intensive and increases the time required for collection, extending the holding time of oocytes that delays their maturation. The aim of this work was to develop an effective method for collecting equine oocytes combining the feature of aspiration (fastness) with that of scraping (high recovery rate of cumulus-intact oocytes). Furthermore, we examined differences in cumulus morphology and maturation rates, comparing this technique to aspiration and scraping, with or without tunica albuginea removal. Collection by vacuum pump aspiration was performed using a 16 g needle while the combination of aspiration and scraping was performed using a Tuohy needle (16 g) that is usually employed for inserting an epidural catheter and its tip shape is similar to a small curette. In unpeeled ovaries, the recovery rates by the Tuohy needle was higher (p < 0.05) than in the 16 g needle aspiration and in the scraped ovaries (57% vs. 36% and 47%) while the rate of cumulus-intact oocytes was higher than aspiration (46.9% vs. 39.36%) but lower than scraping (46.97%) (p < 0.001). In unpeeled ovaries there was no difference in maturation rate of oocytes recovered by Tuohy needle in respect to scraping in peeled ovaries (58.54% vs. 58.24% respectively; p < 0.05). In conclusion, combination of aspiration and scraping by Tuohy needle allows a faster and reliable collection of oocytes suitable for horse IVM.