Transvaginal ultrasound‐guided follicular aspiration of equine oocytes

Abstract

Summary Follicular aspiration was performed in 30 cyclic mares during each oestrus and every dioestrus in which >4 follicles 10–15 mm in size were present. During the final oestrous cycle, 15 mares were superovulated with crude equine pituitary extract before aspiration. With the oestrous mares (99 preovulatory follicles yielding 62 (63%) oocytes) 3 follicular aspiration techniques were examined: a 12‐gauge double‐lumen needle, allowing continuous rinsing of the follicle, provided the best oocyte recovery, 36/43 (84%) compared with the single‐lumen needle (24/47; 51%) or the wire‐loop technique (2/9; 22%) (P<0.05). During dioestrus, 71 oocytes were recovered from 323 follicles (22%): oocyte recovery was not affected (P>0.05) by aspiration technique performed (16‐gauge needle with simple or continuous rinsing). Follicles <15 mm in size gave higher (P<0.05) oocyte recovery rates 36/118; 31%) than did follicles >20 mm in size (3/38; 8%). In the superovulated mares 22 oocytes were recovered from 36 preovulatory follicles (61%). We suggest that transvaginal ultrasound‐guided follicular aspiration is a low‐risk, repeatable method for in‐vivo collection of equine oocytes.