Ref: TCP-12 This Rapid Canine Progesterone Kit is an excellent tool for timing canine ovulation.. The visible signs of heat and breeding time (such as vulval swelling and end of vaginal discharge or flagging) are only an approximate indication of the time of ovulation. These signs can vary by more than a week! Ovulation is triggered by the Luteinizing Hormone or LH which peaks two days before ovulation. Progesterone levels begin to rise at the same time as the LH surge. Ovulation occurs two days after the initial rise in progesterone. Predicting ovulation is done accurately by detecting the initial rise in progesterone. After ovulation occurs, the ovacytes take 2-3 days to ripen, making the most fertile period 5-6 days after the initial rise in progesterone. With the Canine Progesterone Kit is possible to detect the initial rise in progesterone and thus optimise the bitches breeding cycle.