If you ask your veterinarian at what age it is best to spay or neuter your dog or cat, most will probably have an answer of between the ages of 6-9 months (or for simplicity, under 1 year of age), with an emphasis on spaying female pets before their first heat cycle. If you adopted your furry friend from an animal shelter, most likely this task has already been taken care of. But what if you didn’t? Should all pets be spayed and neutered at the same age? Recent studies have brought to light that choosing the appropriate age for your pet to be spayed or neutered may not be so simple.
Numerous studies have been performed over the years showing risk in intact versus neutered pets for developing certain diseases. For instance, there have been many studies that support the fact that female dogs and cats that remain sexually intact are at a much greater risk for developing malignant mammary gland tumors (one study has indicated the risk is 7 times higher than spayed dogs and cats). Female dogs and cats that remain intact are also at a higher risk for pyometra (uterine infection). Additionally, testicular cancer can only occur in intact male dogs, and is usually curable with neutering (most testicular cancers are not malignant). Other problems that can arise with leaving male pets intact include hyperplasia (enlargement) of the prostate gland and prostatitis. Intact male cats that are allowed outside are more likely to roam, get into fights with other cats, and spread disease.
So we know it is important to spay and neuter our pets. Here’s where the decision making on when gets murky though. Over the past ~10-20 years, different studies have come out showing a correlation between early neutering and spaying and some orthopedic abnormalities. It is known that closure of the growth plates present in the long bones of dogs and cats is controlled in part by sexual hormones. If an animal is spayed or neutered prior to growth plate closure, that closure will be delayed, which can result in the bones growing longer than would be normal for that animal. These studies are investigating whether or not those longer limbs are setting up the animal for problems, such as an increased risk of rupture of the cranial cruciate ligament in the knee. Other orthopedic abnormalities, such as bone tumors and hip dysplasia, are being investigated as well.
So where does this leave you and your pet? We recommend that this decision be made after having a detailed discussion with your veterinarian about your pet, its risk for potential inherited and acquired diseases, and its lifestyle. For the majority of cases, it is likely your veterinarian will still recommend the standard age of 6-9 months, since there is still much research to be done, and since we know, at least for female pets, the risk of mammary cancer is much higher in those that go through heat cycles over those that do not. There is no textbook answer to the question of when is the best age to spay or neuter your pet anymore; the decision needs to be made on an individual basis. Please speak to your veterinarian at Twin Maples Veterinary Hospital with any questions related to spaying and neutering your pet.
The following links are for abstracts for some recent studies highlighting risk for spay/neuter and orthopedic abnormalities: