Once a dog comes in heat when do they become furtile?

A female dog is fertile during her heat cycle, which is also known as estrus. This period typically lasts around 9 days, although it can vary between breeds and individual dogs.

Here's a breakdown of the stages of a dog's heat cycle and when she is fertile:

* Proestrus (pre-heat): This stage lasts around 7-10 days and is characterized by swelling of the vulva, bloody discharge, and increased attention from male dogs. The dog is not yet fertile during this stage.

* Estrus (heat): This is the fertile period and lasts for about 9 days (can be shorter or longer depending on the dog). During estrus, the vulva will swell further, the discharge will become clear and watery, and the dog will accept male dogs for mating.

* Diestrus (post-heat): This stage lasts for about 60-90 days and is characterized by a decrease in the discharge, a return to normal vulva size, and the end of fertility.

* Anestrus: This is the resting phase of the cycle and can last for several months. The dog is not fertile during this time.

It's important to note that these are just general guidelines. The exact length of each stage can vary depending on the individual dog. If you are unsure about your dog's heat cycle, it's best to consult with your veterinarian.