Oestrus is the mating period of female animals. When oestrus occurs, animals are said to be ‘in heat’ or ‘in season’. Cats normally have their first oestrus between 5 and 10 months of age, with the average age around 6 months.
The female cat has 2 to 4 periods of oestrus, each lasting 15 to 22 days every year. If she is bred, oestrus seldom lasts more than 4 days.
If successful mating does occur, oestrus may last for 7 to 10 days and reoccur at 15 to 21 day intervals. It is possible for an unmated female to cycle every 3 to 4 weeks most of the year long.
Cats also have oestrus period 1 to 6 weeks after giving birth, so it is possible for a female to be nursing one litter while pregnant with another.
Since there is usually no obvious vaginal discharge or swelling of the genitals, as seen in dogs, behavioural changes are the signs that your cat is in oestrus.
A cat in oestrus carries her tail off to one side, keeps her hindquarter elevated, exhibits ‘treading’ movements of the hind legs and seems unusually affectionate. She spends a good deal of time rolling on the floor and seems much more restless than usual. The cat’s voice seems more piercing than usual and ‘calling’ occurs 1 to 2 days before she accepts the male.
© Forrest Hill Vets (2000) Ltd