When Does a Female Dog Come Into the Time to Mate?

The time female dogs want to mate is called coming into season, going into heat or coming into estrus. This is the only time a female dog will be fertile. Female dogs usually come into season twice a year from the time of their first heat until they die or have been spayed. The time of her first heat differs from dog to dog but on average occurs when she is six months old.

  1. First Heat

    • Female puppies go through their first heat any time from 6 to 24 months, according to the ASPCA. Giant breeds of dogs such as the Saint Bernard tend to go into heat at the longer end of the scale than smaller dogs. Puppies can go into heat as young as four months old, notes "Dog Owner's Veterinary Handbook." In order to avoid unwanted pregnancies, healthy female puppies can be spayed as young as 6 weeks old, according to the American Veterinary Medical Association.

    Time Frame

    • A female dog or puppy stays in heat for 18 to 21 days. However, she will only allow a male dog to approach her for about nine days. During this receptive period, she is actually only fertile for two or three days. The best time to breed the female dog or to artificially inseminate her is three to five days after her luteinizing hormone or LH level hits the 2.5 nanograms per milliliter. Female dogs need their LH levels tested every day they are in heat in order to determine when best to breed.

    Behavior

    • A female dog in heat disrupts regular family life and often needs to be kept in a commercial kennel away from all male dogs in order to be assured that she is not bred. The female dog emits powerful pheromones that draw in male dogs from miles away. During estrus, the female dog usually becomes more timid, has difficultly following basic commands and urinates more than usual.

    Warning

    • Never breed female dogs during their first heat, advises "Dog Owner's Veterinary Handbook." The still-growing puppy cannot physically handle the demands of raising a litter without harming herself or her puppies. Wait until the female dog is between 18 to 24 months old before breeding or undergoing artificial insemination.