Ultrasound-guided follicle aspiration: Effect of the frequency of a lineartransvaginal probe on the collection of bovine oocytes

The effect of the frequency of an ultrasonic linear transvaginal probe; on the collection of bovine oocytes by transvaginal ultrasound-guided follicle aspiration was investigated. Probes with different frequencies (7.5 or 5.0 MHz) were applied to examine the clarity of follicles on the monitor using ovaries of slaughtered cows in Experiment 1. The follicles were visualized on the monitor and divided into small (3- to 5-mm diameter) and large (6- to 10-mm) groups. They were also divided into 2 groups according to the cla rity of their outline (clear or obscure). The number of small follicles vis ualized with a clear outline was greater (P < 0.01) with the 7.5 MHz probe than with the 5.0 MHz probe (9.0 vs 3.2). Oocyte aspiration from live cons a as performed using the 7.5 or 5.0 MHz probe in Experiments 2 and 3. The r ecovered oocytes were divided into 3 categories: cumulus-oocyte-complexes ( COCs), denuded oocytes and all others. In Experiment 2, the number of oocyt es collected per donor cow was assessed, and in Experiment the number of oo cytes per aspirated follicle was examined by aspirating a constant number o f follicles per aspiration session. The numbers of oocytes and COCs per don or con obtained with the 7.5 MHz probe (11.2 and 9.0, respectively) were gr eater (P<0.01) than those obtained with the 5.0 MHz probe (4.3 and 3.5). Th is was also true for recovery rates (81.7 and 65.8% vs 14.2 and 35.8%; P<0. 01). This difference between probes was due to the greater clarity of the f ollicle images obtained with the 7.5 MHz probe. (C) 1999 by Elsevier Scienc e Inc.