Comparison of endocrine changes and ultrasound as means of identifying ovulation in the bitch

Twenty bitches were monitored through pro-oestrus and oestrus using both circulating plasma hormone levels and ultrasonic examination of the ovaries. Using luteinising hormone (LH) as being the generally accepted optimum indicator of the day of ovulation, comparisons were made of the accuracy of progesterone and ultrasound to identify ovulation. Progesterone agreed with LH in 12 of 20 bitches and was within one day in seven of the other eight. Ultrasound was less accurate in that only four of the 16 estimates agreed, with a further six being within one day. However, if only the bitches which were examined by ultrasound with the latest equipment were included, while only three of 11 coincided, six of the remaining eight were within one day of the LH estimated ovulation. It is concluded that, at present, of the rapid assessments, the measurement of plasma progesterone is a better estimator of ovulation than ultrasound.