Spaying and Neutering Your Pet: When Is the Right Time?

February 27th 2018


As many of us understand, there are numerous reasons why our pets should be spayed or neutered and one of the most frequently asked questions from our clients is: “Doc, when is the best time to spay or neuter my pet?"

And our answer is, “It depends!"

In this post, we will provide you with some considerations to help you decide the best timing to spay/neuter your pet because the answer can vary, depending on the circumstances.

To recap, the term "spaying" refers to the removal of the reproductive tract in females, whereas neutering applies to males.

Let’s get started.

Spaying and neutering can reduce cancer and infection of the reproductive organs

In female dogs, spaying has the benefit of reducing the risk of breast cancer later in life. The chance of getting breast cancer increases as such:

- by .5% when spayed before the first heat

- by 8% when spayed after the first heat

- by 26% when spayed after the second heat

Overall, intact female dogs have a seven times higher chance of developing breast cancer compared to spayed females.

In cats, breast cancer is reduced:

- by 86% when spayed before one year of age

- by 91% when spayed before six months of age

Bacterial infection of the uterus and testicular cancer are prevented:

- by 100% by spaying/neutering, however timing is not of any influence

In male dogs, neutering reduces the risk of prostate gland enlargement and subsequent infection at an older age – so the timing of neutering is only of importance at an older age.

Therefore, spaying should be performed before the first heat for female dogs and before six months of age for cats in order to reduce the risk of breast cancer and to prevent infection of the uterus. Neutering should be done to prevent testicular cancer and prostate gland issues.

The effects of spaying/neutering on physical development

Physical development is generally completed when your cat or dog is just over one year old.

Sex hormones stop the musculoskeletal growth process, but stimulate the growth of the urinary and reproductive tract. If pets get neutered/spayed before the production of sex hormones start, they tend to get a bit taller than their intact counterparts.

Moreover, recent research in large breed dogs has shown that this increase in height when neutered/spayed before puberty comes with a mild increase in joint problems such as hip dysplasia and arthritis. A possible explanation for this would be that their joints have to carry more weight than intended causing accelerated degeneration of the joints.

Sex hormones in particular are responsible for the development of the urinary and reproductive tract. If neutered early, the urinary tract tends to stay smaller and is more susceptible to blockages, this is especially true for male cats.

Consequently, to optimize the growth and development of both musculoskeletal and urinary systems, spay or neuter surgery should be performed around one year of age.

Risks of the spay/neuter surgery – the veterinarian’s perspective

Spaying and neutering is performed under general anesthesia, hence there is are risks of anesthetic complications, not unlike in humans. Having said that, veterinarians have greatly decreased the risks associated with anesthesia because of more diligent risk assessments, better anesthetic drugs and improved monitoring prior, during and after general anesthesia.

Because an entire organ (ovaries and uterus) is removed from the body, a spay surgery carries the risk of bleeding. To reduce this risk as much as possible, spaying before puberty or when the pet is not in heat is preferred since less blood flow will be going to the uterus and ovaries and thus the chance of complications due to bleeding is lessened.

Puppies and kittens can be spayed or neutered as early as six to 14 weeks of age, provided extra care is taken with the anesthesia. On the other hand, adult dogs can still be spayed without complications so long as care is taken to ensure that all larger blood vessels are ligated properly; it is for this reason that these surgeries typically take a bit longer.

Spaying an animal in heat increases the risk of the surgery significantly, because blood flow to the uterus is increased as is the size of the uterus. Therefore, spaying is preferably not done when the cat or dog is in heat! If you apply this argument to the neuter: once the dog or cat is sexually active, there is increased blood flow to the testicles and the risk of bleeding during or after the surgery increases mildly.

One argument in favour of spaying and neutering around six  months of age is that is when most dogs have all of their permanent teeth. When they are under anesthesia for the spay/neuter and all of their permanent teeth are in, any remaining baby teeth can be extracted to prevent future dental issues. Spaying or neutering should be done before the start of puberty to reduce the risk of the surgery, but after all permanent teeth have come in.

Is spaying/neutering a fix for behavioural issues?

Discerning the behavioural impact of spaying and neutering is less obvious than you might think. Behavior is determined by various factors such as breed, genetics, socialization and training (or lack thereof), environmental factors, physical conditions and sexual development.

With the start of the production of sex hormones comes the onset of puberty and related behaviors including urine marking, mounting, roaming and potential inter-dog aggression. Spaying and neutering may or may not have an impact on these behaviors and should be carefully considered while co-examining the other factors affecting behavior. In some cases, such as aggression, spaying and neutering might actually make the behavior worse!

So whether or not to perform the procedure should be determined by looking at the various factors affecting behavior. The best advice we can give you is to consult with a veterinarian who is well versed in behavior or a veterinary behaviorist.

Weighing the pros and cons of spay/neuter timing

There is no straightforward answer when it comes to the question of when to spay or neuter your pet. Clearly many factors do play a role and only some will apply to your pet’s particular situation.


Also, If you have questions about spaying or neutering your pet, please call to book an appointment with one of our vets. Our phone number is (403) 615-8016.

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