1 Retained by their creators or by archive service providers, such as national or local government archives, university archives, or other archives that collect and maintain archives of other organisations. 2  A great national resource as they document the history and identity of communities throughout the country.
Although six months old is the average age of a dogâs first heat, this can vary widely. Some dogs can go into heat as young as four months, while larger breeds may be as old as two years before their first heat. Responsible breeders never breed a dog on her first or even her second heat. It is considered best practice to wait until her third heat, at about 18-24 months.
Usually your dog will go into heat every 6-7 months though again each dog is different and can go back into heat as early as 4 months or not for 12 months. Most however are average. During the first part of a dogs heat period you will notice swelling of the vulva, possibly an increase in urination and bleeding.