BREEDING: PROGESTERONE
However, tests do exist to determine a peak period for successful mating. One of the most reliable is a test which monitors progesterone levels in the blood. Progesterone is a male hormone found in every female, to lessor amounts than in males.
A bitch about to be bred will experience a significant drop in progesterone levels just as she begins to ovulate. Knowing the drop has occurred alerts most breeders that active breeding should begin.