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At what age do puppies go into heat?

Updated on June 29, 2010

Surprise! Surprise! The puppy that has sulked in its crate has magically produced a litter of furry puppies overnight. The puppy is no longer a puppy after all! At what age does a puppy go into heat? Breeds of dog vary not only in appearance, in personality and temperament but in reaching sexual maturity as well. Small breed sexually mature earlier as compared to other large breeds. Small breeds are noted to go into first heat at the age of 6 to 12 months. Large breeds on the other hand go into first heat at 1 to 2 years of age. Would you believe, dogs generally mature sexually at 6 months to one year but mature socially at about 2 years of age?

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The "heat" cycle of a dog

Estrus, in heat or in season…these are the different terms used to describe the mating period of canines. As mentioned, breeds of dogs differ in a lot of ways and one of these is the reproductive cycle. Generally, dogs would go into first heat at 6 to 12 months of age. Large breeds though are known to sexually mature much later. A German Shepherd for instance will come into its first heat at 12 to 24 months of age. The occurrence of estrus is fairly consistent in a particular dog but greatly vary between breeds. Some breeds would go into the estrus cycle once every 4 months while some breeds like the Basinji would only have one in heat period in a year.

Symptoms of canine reproductive cycle stages

Canine reproductive cycle is divided into four stages – proestrus, estrus, diestrus and anestrus. In the proestrus stage vaginal bleeding and swelling of the vulva will be noticed. The bitch will emit a distinct smell that agitates male dogs. On the estrus stage, vaginal discharge will be yellowish rather than bloody. It is during this stage that the bitch will allow to be mated. Diestrus is the period of ovarian activity thus no symptom will be seen. This period will last until the dog whelped after which it will enter the final stage anestrus. This stage would usually last 4 to 5 months until the dog enters the proestrus stage again.

Estrus period

Again, the estrus period differs from one breed to another. The heat period normally lasts from 8 to 30 days although the average for most dogs is 20 days. On the first 7 days, the dog will be coming into heat; the next 7 days, the dog is in heat and the last 7 days, the heat period will be waning. The pet is considered to be in heat during the whole period but the bitch will not accept a male dog until it is on the 10th to 16th day after the cycle has started. It is during this period that pregnancy will occur.

Reproductive capability

Dogs will remain fertile even in advanced age. However breeding dogs of advanced age are not recommended as apart from whelping difficulties, there is a possibility of small litter size.

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How to Care for a Dog in Heat

Signs of Pregnancy


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