The lengthening daylight hours of spring and summer cause the queen to come into oestrus (i.e. into season) and the autumn daylight pattern stops cycling. Breeds such as the Siamese and Burmese may cycle throughout the year.
Surgical removal of the ovaries and uterus is usually done before they come into their first oestrus, which occurs at about 5 or 6 months.
Males are usually castrated by the time they are 6 months old.
A slow release progesterone hormone "Covinan" is available. It is injected at various intervals to prevent the queen coming into oestrus.
"Suprelorin", a new inhibitor of ovarian function, is now avavilable on the market.