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Oestrus - Canine

Oestrus is the mating period of female animals.  When oestrus occurs, animals are said to be ‘in heat’ or ‘in season’.  Dogs generally have their first oestrus cycle at 7 to 12 months of age.  Some individuals of the large breeds however may not have the first season until they are 12 to 14 months of age.

The complete cycle takes about 6 months with 2 oestrus periods each year.  There is individual variation in this, but given a female’s pattern tends to be repeated regularly.

The oestrus cycle can be divided into four stages:

This stage begins with the appearance of vaginal bleeding.  It normally lasts from 4 to 9 days.  Male dogs will be extremely interested in the female, however, she will not accept him for breeding.

This is the stage in which the female will accept the male and conception can occur.  The discharge is more yellowish than bloody.  Ordinarily, the stage lasts for 4 to 13 days.

These two stages are periods of ovarian activity.  No special symptoms occur.  False pregnancies frequently occur during metoestrus.


You should consider your pet to be ‘in season’ for 21 days: 7 days coming into heat, 7 days in heat and 7 days going out.  Although conception is most likely during the middle 7 days ‘mother nature’ doesn’t always follow the rules, so confine your pet for the entire three weeks.

Remember that the above information is ‘general’.  Not all females follow these patterns.  Consult your veterinarian 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 the outcome.

© Forrest Hill Vets (2000) Ltd