Desexing or sterilisation is a surgical procedure that removes both the ovaries and the uterus in female cats (ovariohysterectomy), meaning that they are no longer able to come on heat and become pregnant.
The Cat Act 2011 states that cats that have reached 6 months of age must be sterilised by a veterinarian, unless the cat is exempt from sterilisation. A cat can only be exempt from sterilisation if a certificate is given by a veterinarian or the cat is owned by an approved breeder for breeding purposes. The penalty of non compliance is a fine of $5 000.
Apart from being law and the prevention of unwanted kittens, desexing also has a number of medical benefits for your cat. These include preventing inflammation of the uterus (metritis), uterine infection (pyometra), ovarian cysts and tumours of the reproductive system.
Many people decide to get their female cat desexed as they are concerned about her getting out when she is on heat. Not only is there a risk of her getting pregnant, but there is also a very high risk of her getting hit by a car or getting injured as her only focus is on finding a male to mate with. There is also a risk of picking up one of the potentially fatal feline viruses (feline Leukaemia or feline AIDS).
If your female cat comes in to season before you have had a chance to have her desexed, keep her inside and separated from any entire male cats. If she does manage to escape and mate, your veterinary health care team will be happy to provide advice on options available (in most situations sterilisation will still be an option) and they will most likely wish to test for FIV (feline AIDS) and FeLV (feline Leukaemia) if the male tom cat is unknown.