Estrus ("heat") is the mating period of female animals. When
estrus occurs, animals are said to be "in heat" or "in season." Dogs
generally have their first estrous cycle at 6-12 months of age. Some
females of the large breeds, however, may not have their first estrus
until they are 12-24 months of age.
The complete cycle takes about 6 months, resulting in 2 estrous
periods each year. Individual variation occurs, but a given female's
pattern tends to be repeated regularly.
The estrous cycle can be divided into 4 stages:
1. Proestrus: This stage begins with the appearance of vaginal
bleeding. It normally lasts from 4 to 9 days. Male dogs become very
interested in the female; however, she will not yet mate with them.
2. Estrus: This is the stage in which the female will accept the
male and conception can occur. The vaginal discharge is more
yellowish than bloody. Ordinarily, the stage lasts for 4 to 13 days.
Your female will stand still and hold her tail to the side when you
touch her back or a male dog tries to mount.
3. and 4. Metestrus and anestrus: These 2 stages are periods of
ovarian activity, but with no significant outward signs. False
pregnancies frequently occur during metestrus.
Some Important Points
* You should consider your pet to be "in season" for 21 days: 7
days coming into heat, 7 days in heat, 7 days going out. Though
conception is most likely during the middle 7 days, Mother Nature
doesn't always follow the rules. Confine your pet for the entire 3
* Remember that the above information is general. Not all females
follow these patterns. Consult with the doctor if your pet does not
seem typical. Sometimes, cycling problems can be an early warning of
more serious problems, and the sooner they are dealt with, the