Now that the City of Los Angeles has passed an ordinance requiring that cats and dogs over the age of four months be spayed/neutered, it is of course the law that we do so. But long before any such law was passed we still had plenty of reasons to do so, and NO good reasons not to. And because this weekend is the Winter Solstice (a very auspicious date in the feline reproductive calendar), what better time to address the subject?
Cats are seasonal breeders. The females begin coming into estrus ("heat") when the days start getting longer at the solstice. Intact male cats pick up on olfactory and behavioral cues and get rather testy about defending their turf from other males (and other cats in general) when the breeding season begins. So this time of year we hear a lot of caterwauling and fighting outdoors, and abscesses due to bite wounds skyrocket in frequency.
Spaying (ovariohysterectomy in females) and neutering (can apply to either but generally used to refer to castrating males) are important in avoiding cat fights and the resulting injury and illness. Of course, they are also the means by which we decrease pet overpopulation. Few people can take much in the way of a female cat in heat's yowling and carrying-on, and fewer still can tolerate the pungent reek of intact tomcat urine - fortunately neutering solves these problems.
Male cats, if not neutered in a timely manner, WILL begin to spray their urine as a territorial marking behavior. And female cats if allowed to go through repeated heat cycles will be at drasticallly increased risk for mammary cancer down the road.
Our recommendation is to neuter the males at 8 months of age. We feel that it is critical for them to approach puberty - sex hormones are importent in physical development and neutering too early puts the cat at risk of hip fractures, urinary obstruction, and possibly obesity and diabetes. It is extremely rare for tomcats to begin spraying before 10-12 months, so we have a margin of safety built in (and if spraying does begin, neutering stops it cold in 99% of cases).
We advise owners to spay female cats at 6 months of age - most cats will not be coming into estrus before that age, and if they do it need not delay the surgery at all. It is very important to keep them indoors at all times until they have been spayed because we do NOT want them to get pregnant - spaying a pregnant cat can be very expensive and quite dangerous for her.
If you live in the City of Los Angeles and are concerned about running afoul of the new ordinance by delaying surgery, please feel free to discuss this with me. I put a premium on doing the surgery at the time that is most medically appropriate for my individual patients, and can issue a letter of exemption provided that you follow my advice on when to do the procedure and keeping the cat indoors at all times beforehand.