Plasma LH and progesterone levels before and after ovulation and observation of ovarian follicles by ultrasonographic diagnosis system in dogs

Recently, canine frozen semen has been attracting attention for breeding pu rposes, and methods of judging ovulation and optimum timing for inseminatio n have become important. As methods of predicting the canine ovulation, vag inal smear, plasma sex hormone levels and ultrasonographic diagnosis system (US) have been investigated in combination, but a standard technique has n ot yet been established. Therefore, we investigated a method of predicting canine ovulation in dogs by US, and by measuring plasma LH and progesterone (P) levels three times a day. Ovulation could be observed by detecting irr egularly shaped ovarian follicles by US in six of 11 dogs (54.5%). In these dogs, the time between the LH peak and ovulation was 24-48 hr, 38.0 hr on average. The P level on the ovulation day was 1.88-2.81 ng/ml, 2.34 ng/ml o n average. A value of 1.88 ng/ml was detected in one dog, but the other fiv e dogs showed P levels of 2 ng/ml or higher. The P level on the day before ovulation was 0.8-1.56 ng/ml, 1.12 ng/ml on average. Assuming that ovulatio n occurred two days after the LH peak in the 11 experimental dogs, the P le vel was 2.12-4.06 ng/ml, 2.78 ng/ml on average. The period of a high LH lev el, not less than 10 ng/ml, continued for 12 hr around the LH peak. Based o n these findings, to predict ovulation using US and LH level, it would be n ecessary for the tests to be performed several times a day. In contrast, it was shown that the day on which a plasma P level of 2 ng/ml or higher was detected by the test performed once a day corresponded to the ovulation day .