How to Collect Equine Oocytes by Transvaginal Ultrasound-Guided Follicular Aspiration

Assisted reproductive techniques such as oocyte transfer and intracytoplasmic sperm injection (ICSI) can be used clinically to produce foals from mares with reproductive abnormalities that prevent normal breeding or production of embryos. ICSI can also be used to produce foals from stallions with poor fertility or from semen with limited quantity. Both of these procedures require the collection of oocytes. Ultrasound-guided transvaginal oocyte aspiration (TVA) can be used by the practitioner to recover maturing oocytes from dominant gonadotropin-stimulated follicles (DSF) or immature oocytes from smaller or subordinate follicles (IMM) for use in these techniques. DSF oocytes are generally required for oocyte transfer, whereas both DSF and IMM oocytes are suitable for ICSI. Once collected, the oocytes can be used on-site or shipped to a referral laboratory for embryo production.