Anovulatory ovarian cycles in dogs.

In 14 of 1152 female dogs, monitored and prepared for mating during the last 2 years, a functional disturbance of the ovaries on the basis of vaginal inspection, cytological investigation of vaginal smear and progesterone concentration was observed, manifested by anovulatory sexual cycles. After a normal pro-oestrus of approximately 8-16 days the bitches showed an increase in progesterone concentration to 6.4-9.5 nmol l-1 and in two cases 11.0 nmol l-1, followed by a sudden decrease to the basic rate of 0.64 nmol l-1, associated with all clinical signs indicative of the regression of oestrus. These findings suggest that reliable identification of mating time in female dogs requires monitoring of rising progesterone concentrations up to at least 32.0 nmol l-1.