People who have adopted a new pet often wonder about the ideal time to spay or neuter their cat or dog. In fact, questions of this nature are among the most common that I receive through Dogster and Catster.

A recent and very lengthy survey in the Journal of the American Veterinary Medical Association (JAVMA) served as a comprehensive review of available information on the subject. And there is a great deal of information. The article cites 183 sources.

Sadly, even 183 sources are nowhere near enough to sort through a subject this complicated. The authors final conclusion is that there is no particular age that can be considered the best age for spaying or neutering a pet.

The most basic decision to make regarding the timing of spay or neuter surgery is whether to perform the surgery before or after the pet reaches puberty. Surgeries performed before puberty are sometimes called early spays and neuters.

Some of the benefits of early spaying and neutering include decreased surgical time and lower rates of surgical complications (it is simpler to spay or neuter an animal that is not fully grown). Females that are spayed before their first heat are at no risk of pregnancy and almost no risk of breast cancer. Males are less likely to become aggressive.

However, there is some evidence that early spays and neuters may contribute to obesity later in life (other evidence suggests that they do not). As well, dogs that undergo surgery early in life may be at increased risk of knee injury and hip dysplasia.

The more you research the subject, the more confusing it becomes. Pets that are spayed or neutered early may be less likely to suffer from separation anxiety, but more likely to suffer from fear of noises. They suffer lower rates of some cancers (breast, testicular, ovarian, uterine) and higher rates of others (prostate, bladder, bone). They are more likely to develop incontinence, and less likely to develop prostatitis.

So, what is the best course of action? The preponderance of the evidence suggests that performing spays and neuters before puberty is whats best. But it is not an open-and-shut case.

I recommend that you find a good vet who is willing to discuss your pets situation. Since no formula can provide an answer regarding the ideal timing of spays and neuters, your best bet is to work with your vet to time the surgery based on your pets lifestyle, needs, and breed.

The survey cited in this post is J Am Vet Med Assoc 2007;231:1665 – 1675