REPEATED TRANSVAGINAL OOCYTE ASPIRATION IN UNSTIMULATED AND FSH-TREATED MARES

Transvaginal ultrasound-guided follicular aspiration was conducted rep eatedly in 5 cyclic mares. Three techniques were used and the aspirati ons were performed either greater than or equal to 23 d apart (Al, B1, C1) or 6 d apart (A2, B2,C2). During the Al and A2 aspirations, the f ollicular cavity was flushed manually 8 to 10 times with flushing medi um-filled (60 ml) syringes, while an electrical aspiration pump was us ed for the B1, B2, C1 and C2 aspirations. Prior to aspirations C1 and C2, the mares were treated daily with porcine FSH (100 mg, im) for 4 d . Aspiration was conducted 24 h after the last FSH injection. A total of 212 follicles with diameters varying between 5 and 23 mm was aspira ted. The oocyte recovery rate was significantly higher (P=0.004) from aspirations conducted with a greater than or equal to 23-d interval (3 5.8%) than from those aspirated 6 d after the previous aspiration (18. 4%). Mode of evacuation and flushing (pump or syringe) and FSH treatme nt of the mare had no detectable effect on the oocyte recovery rate or on the cumulus dimensions of the aspirated oocytes. More than 80 % of the oocytes were at the germinal vesicle or diakinesis stage. (C) 199 7 by Elsevier Science Inc.