Ultrasound-guided follicle aspiration: effect of the frequency of a linear transvaginal probe on the collection of bovine oocytes

摘要

In experiment 1, probes with 7.5 or 5.0 MHz frequencies were evaluated for their clarity of follicle image on the monitor using ovaries of slaughtered cows. The follicles were visualized on the monitor and divided into small (3-5 mm diameter) and large (6-10 mm) groups. They were also classified by the clarity of their outline (clear or obscure). The number of small follicles visualized with a clear outline was higher (P<0.01) with the 7.5-MHz (9.0) than with the 5.0-MHz (3.2) probe. Oocyte aspiration from live cows was performed using the 2 probes in experiments 2 and 3. Oocytes recovered were divided into 3 categories: those with cumulus-oocyte complexes (COCs), denuded oocytes and others. In experiment 2, the number of oocytes collected per donor cow was assessed, and in experiment 3 the number of oocytes per aspirated follicle was examined by aspirating a constant number of follicles per aspiration session. The numbers of oocytes and COCs per donor cow obtained with the 7.5-MHz probe (11.2 and 9.0 respectively) were higher (P<0.01) than those obtained with the 5.0-MHz probe (4.3 and 3.5). This was also true for corresponding recovery rates (81.7 and 65.8% vs. 44.2 and 35.8%; P<0.01). This difference between probes was attributed to the greater clarity of the follicle images obtained with the 7.5-MHz probe.