Progesterone in Dogs: Assessment of Heat and Whelping For dog breeders, one of the most difficult parts of breeding can be identifying the right time to mate. Female dogs usually have just two seasons a year, and the fertile window can be very small. Even though a bitch might show bleeding and behavioural signs of heat for over 2 weeks, her fertile window might be as narrow as just a few days. progesterone testing is one of the ways breeders…