If you own more than one dam, they will usually cycle together; one dam in heat will bring other dams into heat.
A female should NEVER be bred on her first heat (she has immature eggs) and preferably not her second either. The rule of thumb that works best is to breed on the third season, or at one and a half to two years of age, and after all health tests have been passed.
Small vulva—dam not in heat
A female dog in full-standing heat swollen up
A dam in heat and almost ready to be bred. You really need to stand your girl up, and look at the vulva. It will tip upwards and change position slightly to make it easier for the male to penetrate, also if you insert a gloved finger it will squeeze your finger inward. When a female ovulates, she will try to mount the male. She will have a very STRONG, distinct smell that dogs from MILES around can smell. Her discharge will have changed from bright red to a more yellow color.
Dam in heat. The vulva is swollen, sticking out from the body and three times the normal size.
Female dog in heat
Female dog in heat dripping blood and vaginal fluid.
Other signs of being “ready to breed, ” are her willingness to stand for the male and she will hold her tail off to the side, called “flagging.” She will often back her butt up to your leg as well..
A vet has ways to tell when she is fertile, but you still have to watch for the swelling and bleeding.
You will notice after her first heat that her teats will be more noticeable.