When do female Newfoundland dogs go into heat?

Newfoundlands do not have a heat cycle like other female dogs. Instead, they experience an estrus cycle, which is similar to the menstrual cycle in humans. The estrus cycle in Newfoundlands typically lasts for 21 days and is divided into four stages:

1. Proestrus: This stage typically lasts for 3-7 days and is characterized by vaginal bleeding and swelling of the vulva.

2. Estrus: This stage typically lasts for 5-10 days and is characterized by increased receptivity to males. The female Newfoundland will stand with her tail to one side and may yelp or squeal when approached by males.

3. Diestrus: This stage typically lasts for 10-14 days and is characterized by the decline of estrogen levels and the preparation for the next cycle.

4. Anestrus: This stage lasts until the next estrus cycle begins and is characterized by inactivity of the reproductive system.

Newfoundland females typically come into heat for the first time between 12 and 24 months of age, and they may continue to cycle every 6-12 months throughout their reproductive life.