Female dogs become sexually mature between 6 and 12 months of age. Smaller breeds reach puberty at a younger age than larger breeds. Most dogs go through a heat or estrus cycle every 5 to 10 months (7 months = average). 


The canine heat cycle is divided into several stages based on the dog's behavior and physical signs:

PROESTRUS (pre-heat) = the period of time when a female dog attracts males but is not receptive to breeding. Females usually have a blood tinged vaginal discharge and a swollen firm vulva. Average = 9 days (range = 0 to 17 days)

ESTRUS (heat) = when the female dog will accept the male and stand for breeding. The vaginal discharge usually becomes clear (some dogs will continue to have a bloody discharge throughout) and the vulva less swollen. The bitch will "flag" or hold her tail off to the side when the male approaches. Average = 9 days (range = 3 to 21 days)

DIESTRUS = starts when the female will no longer allow breeding and ends when the ovaries stop producing the hormone progesterone. This period lasts about 65 days in the pregnant dog ending when the puppies are delivered, or 75 to 95 days in the non-pregnant dog. Progesterone may cause many false signs of pregnancy like nesting behavior and milk production even if the dog is not pregnant. "False pregnancy" resolves on its own when progesterone levels decline.

ANESTRUS = period between heat cycles when the uterus becomes smaller and inactive. This is the best time to spay a dog.

BREEDING MANAGEMENT It is best to wait until the third heat period (around 1 1/2 or 2 years of age) before breeding. Successful breeding is more likely if the dogs have had previous breeding experience. Most breeders advise taking the female dog to the male dog, as he will be more comfortable in his own territory. It may help to let the dogs get to know each other before she is in heat. Microscopic examination of vaginal smears is helpful in determining the optimal time to begin breeding. Blood tests which measure female hormones (Leutinizing hormone and progesterone) can also be used to predict when it is the optimal time to breed a dog. These tests are most valuable when artificial insemination is being done or if a bitch has a history of difficulty getting pregnant. Breeding is then allowed every 2 to 4 days until the female refuses to stand for breeding. Successful breeding involves a period of prolonged physical attachment of the male and female due to a localized swelling near the base of the penis (called a "tie"). Do not attempt to pull the dogs apart, this will occur naturally in 5 to 20 minutes.

A veterinarian using palpation and/or ultrasound at about 28 days after breeding can confirm pregnancy.

Average canine pregnancy = 65 days. Range = 57 to 68 days.

Breeding Heat Cycle Whelping Chart Canine Pregnancy

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