By measuring the progesterone levels in dogs, an owner and/or breeder can predict the best time to breed a female dog. Progesterone is the hormone that maintains a pregnancy, while the hormone estrogen stimulates the ovaries into producing eggs. Luteinizing hormone (LH) stimulates the ovaries to release the eggs.
Ovulation Is Important
Ovulation is the release of an egg from the ovaries. This happens in most mammals when the estrogen level in the blood increases. However, ovulation takes place in dogs when the estrogen level declines and the progesterone level increases. The knowledge of the progesterone levels and luteinizing hormone (LH) levels during the female dog's heat can determine the time of ovulation and then the date of birth of the resulting puppies. Testing of the blood must be done every 24 hours, since the LH spike or increase lasts for only 24 hours or less. The spike can be missed if the testing starts too late. This spike occurs usually 48 hours before ovulation.
Progesterone Levels Predict Breeding Results
Progesterone levels should be tested every two to three days once the dog is three to five days into heat. Progesterone levels are usually less than 1.0 ng/ml before the LH spike, rising to 3 to 4 ng/ml the day following the LH spike. When the progesterone level rises to 5 ng/ml, ovulation occurs. Most professional dog breeders use either natural or artificial insemination methods to maximize the success of the breeding.
The type of insemination determines the time frame after the spike in LH levels:
- The best results using natural breeding occur three days after the 2.5 ng/ml progesterone mark is reached. Sperm in fresh semen can survive up to a week after insemination.
- Artificial insemination using fresh chilled semen should be deposited into the cervix for better success, since the semen can be drawn into the uterus. Insemination should occur four days after the progesterone levels reach the 2.5 ng/ml mark, or two days after the 5 ng/ml mark.
- Artificial insemination using frozen semen is usually done during surgery in which the semen is deposited directly into the uterus for best success. This occurs five days after the 2.5 ng/ml mark or three days after the 5 ng/ml mark. Sperm in frozen semen survives less than 24 hours after insemination.
Sperm requires a maturing time of seven hours before it can fertilize an egg, while eggs need approximately 48 hours after ovulation to mature until they can be fertilized. The egg is fertilized in the fallopian tubes and then travels to the uterus before implanting there 17 to 18 days after ovulation.
Pregnancy and Whelping
Progesterone levels continue to increase for two to three weeks after ovulation, reaching 10 to 80 ng/ml. This level remains for about 60 days regardless of whether the dog is bred or not.
Progesterone levels drop to 2 ng/ml about 48 hours before whelping (giving birth), dropping to 1 ng/ml about 24 hours before whelping.