Repeated transvaginal ultrasound‐guided follicle aspiration in the mare

Abstract

SummaryTransvaginal ultrasound‐guided follicle aspiration was performed repeatedly in 5 Dutch Warmblood mares during a time span of 3 months (mid‐June‐mid‐September 1992). During 24 aspiration sessions (4–7/mare), 200 follicles were aspirated and 34 oocytes retrieved, giving oocyte recovery rates of 12.3% and 24.4% when using single channel needles or double barrel needles respectively. There was no significant effect of cycle stage on oocyte recovery rates. Follicle aspiration performed without any hormonal pretreatment gave significantly higher oocyte recovery rates of 26.9%, compared with 8.2 and 15.3% for pretreatments with prostaglandin F2α and human chorionic gonadotrophin respectively. Measurements of daily plasma progesterone concentrations in the mares revealed that follicle aspiration induced luteinisation of the follicles within 1–6 days after aspiration, resulting in a progesterone pattern similar to that of a normal oestrous cycle with ovulation when follicles were aspirated during oestrus, or in prolonged dioestrus in the mares in which follicle aspiration was performed during the luteal phase. The procedure was well tolerated by the animals and no clinical side effects were noted. This technique provides a non‐invasive, relatively simple method for the repeated puncture of multiple immature and preovulatory follicles in the mare and the possibility of obtaining up to 6 oocytes per mare in a single follicle aspiration session.