Technical aspects of transvaginal ultrasound-guided follicular aspiration in cows.

A 7.5 MHz rectal transducer adapted for transvaginal use was compared with a human microcurvilinear 6 MHz transvaginal transducer for follicular aspiration in cows. Some of the problems encountered while developing an accurate and repeatable technique are discussed, including the preparation of the cow, and the selection of the needle and suction apparatus. Proficiency in the retrieval of oocytes was improved through practice. Four cows were aspirated on days 2 to 4, 9 to 12 and 15 to 16 after oestrus in two successive oestrous cycles. The initial recovery rates were poor (7 per cent) and the oocytes were of poor quality, being almost completely denuded. However, after five weeks' practice recovery rates of 41 per cent were achieved and the oocytes were suitable for in vitro maturation.