MSD Manual

Please confirm that you are a health care professional

honeypot link

Breeding and Reproduction of Dogs


John A. Bukowski

, DVM, MPH, PhD;

Susan Aiello


Last full review/revision Jul 2011 | Content last modified Oct 2016
Topic Resources

The reproductive cycle in female dogs has 4 phases. Female dogs that have not been spayed (bitches) typically have 2 estrus or “heat” periods per year (about 6 months apart), each lasting about 2 to 3 weeks. In some dogs, the intervals between estrus are much longer. The first heat occurs between 6 and 15 months of age, depending on the size of the dog (later in larger breeds). Females can become pregnant during their first heat or any later heat period.

Estrous (Heat) Cycle in Female Dogs

  • Proestrus—Start of heat. Lasts 7 to 10 days. Vulva swells and blood flows. Females attract males but will not allow mounting.

  • Estrus—Mating period. Lasts 5 to 10 days. Blood flow lessens and then stops. Females attract and accept males. Ovulation occurs during this time, usually 2 to 3 days after mating.

  • Diestrus. The period 10 to 140 days after heat, when the dog is either pregnant or in a resting phase.

  • Anestrus. The resting period between diestrus and the next heat cycle.

Male dogs do not have a sexual “cycle.” Rather, they respond to females in heat at any time of year. Males are most fertile when fully mature.

Others also read
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Test your knowledge
Disorders of Calcium Metabolism
Calcium, in its ionic form, plays a key role in the function of many body systems. Precise control of calcium ion concentrations in extracellular fluids is regulated by several hormones. Which of the following is NOT involved in calcium homeostasis?
Become a Pro at using our website 

Also of Interest

Become a Pro at using our website