GENERAL INFORMATION

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 month 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 estrus 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 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 & 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 weeks.
• 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 better.

From: Erleweine DVM, Kuhns DVM MS Instructions for Veterinary Clients.