The visible signs of heat and breeding time (such as vulval swelling, 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 accurately done by detecting the initial rise in progesterone.
After ovulation occurs, the ovacytes take 2-3 days to ripen, making the fertile period 5-6 days after the initial rise in progesterone.
With the TARGET CANINE OVULATION Timing kit, it is possible to detect the initial rise in progesterone. The progesterone level before ovulation is low (between 0 and 1.0 ng/mL). This corresponds to a bright blue test result. When the initial rise in progesterone occurs, the test result will be light blue.