A critical evaluation of ultrasonic monitoring of superovulation in cattle.

This study evaluated real time B-mode ultrasonic monitoring for scanning ovaries of cows superovulated using eCG (1500 or 3000 i.u.). Follicular growth was monitored after stimulation and follicles categorized according to size. Numbers of large (> or = 10 mm) follicles correlated weakly (r = 0.31) with numbers of luteal structures formed subsequently. Timing of ovulation was confirmed by comparison with peak LH and plasma progesterone concentrations. Ovulation was visible on scanning but quantitation of corpora haemorrhagica was not accurate in superovulated ovaries. Luteal structures counted at scanning correlated significantly with findings at post mortem (r = 0.75; P < 0.01) but enumeration of structures was inaccurate. Scanning consistently underestimated luteal structures. Numbers of observed luteal structures correlated weakly with embryo recovery (r = 0.36). It was concluded that the presence of luteinized follicles greatly reduced the accuracy of identification of structures in superovulated ovaries.