Should I neuter/spay my dog? When would I do it? Does it affect their learning ability? Does it stunt their growth? Does it stop aggressive behavior? Will it stop male dogs from lifting their leg? Will it stop humping behaviors? All of these burning questions will be addressed below.
If you ask the popular question of “at what age should I neuter/spay my dog”, you will get a huge variety of answers. It seems very few industry experts can agree on the timing. You would think to ask your vet as they have the most education and are the experts, but you’d be surprised how often they disagree with each other. Is there a consensus on when to do it? No. Not that I have found – but I’ll share with you my thoughts having trained over 1400 dogs and been in this industry for 12 years.
If you are not going to breed your dog, it would probably be advisable to neuter/spay them. I’ve had 5 personal dogs and I’ve never neutered/spayed any of them. Why? Well — besides one female dog that succumbed to health problems before turning one year old, I’ve only had male dogs. Most of them were working dogs and neutering a working dog is a no-no. Plus, frankly, I wouldn’t want my balls cut off, so why would I think my dog would want his removed? I know that sounds a little silly, but it’s just how I feel.
If you don’t have a working dog (and most of you will never), and you aren’t going to breed your dog, then I would recommend you neuter once they are done growing and developing. When do dogs finish developing? Usually around the ~18-month marker in life. Once biology has finished doing its thing, then we can play God and have that operation done.
“But Jason! My vet told me to neuter when they are puppies. Why are you contradicting them?”
Unfortunately, because there are so many veterinarians in most cities, part of their revenue stream is completing spay/neuter surgeries. I know that sounds a bit crass, but it’s true. There are 19 Veterinarian offices in Grand Rapids alone. That’s a lot of competition. Their revenue starts with de-worming meds, followed by standard vaccines, rabies (required by law), Distemper, plus they usually push/recommend Bordetella (kennel cough), K9 Influenza, Lepto (if not included in Distemper), plus heart worm preventative, plus flea & tick medicine. You get a puppy at 8-weeks of age and your vet is going to make $XXX amount of money off your puppies needs (I’m not sure what the profit margins are for Veterinarians). Part of that revenue amount is going to be a push to neuter young to “prevent unwanted pregnancies”. That last part is fair, but I think overhyped a tad.
Just know that there is no ‘window of opportunity’ for neutering. You can neuter a dog at any age, but if you do it before they are done growing, science says they are going to experience some side effects.
Are they going to grow as big as they were going to? Will waiting make them larger/taller than they normally would have? Newer research (from UC Davis in 2014), shows that the dog’s risk of joint disorders goes up 2x when you neuter before 18 months of age (not in every breed).
In regards to cancer rates, the data suggests there are differences on timing of neutering between male and female dogs. For example, female golden retrievers, neutering before 6-months of age elevates the risk of one or more cancers 3-4x the level of non-neutered females. On the contrary, male dogs didn’t have much difference in cancer rates for varying ages of neutering.
Researchers at UC Davis School of Veterinary Medicine did studies on specific breeds. If you want to read more about that, click here (https://www.ucdavis.edu/news/neutering-health-effects-more-severe-golden-retrievers-labradors).
If I have a female dog that I do not plan on breeding, then I will spay right after they finish growing. The main reason is due to heat cycles and diaper use which is not fun to deal with.
Does it affect their learning ability?
Short answer: No, not in any meaningful way that I’ve seen in 12 years of training.
I’ve worked with plenty of intact dogs and plenty of neutered ones. The ones that learn fast are the ones with good genetics, solid early socialization, and consistent training. The ones that struggle usually have the opposite. Neutering (or leaving them intact) doesn’t magically turn a smart dog dumb or a hard-headed dog into a rocket scientist.
There is some research floating around that looks at spatial learning and memory tasks. Intact females sometimes edge out the others in certain tests, and early spaying can slightly affect that. But in the real world of everyday obedience, recall, leash manners, and impulse control? It doesn’t matter. Start training your puppy the day you bring them home. Waiting until after surgery is just wasting the best learning window they have.
Does it stunt their growth?
It doesn’t stunt growth — if anything, early neutering can do the opposite.
Sex hormones help close the growth plates in the long bones. When you remove those hormones too early, the plates stay open longer. The dog can end up taller with longer legs than they would have been if left intact. Sounds cool until you realize those longer, lankier bones and joints are also the ones that show higher rates of hip dysplasia, elbow issues, and torn cruciate ligaments — especially in larger breeds.
That’s exactly why the UC Davis research keeps coming up with those 2–4x higher joint disorder numbers when dogs are neutered before 6–12 months. Waiting until roughly 15 months (or later for the giant breeds) lets the skeleton finish what it was designed to do. Then you can neuter without messing with the blueprint.
Does it stop aggressive behavior?
No. And anyone who tells you it does is overselling it.
Neutering can reduce some hormone-driven male-to-male posturing and certain types of sexually motivated aggression. That’s real. But most aggression I see in training has nothing to do with balls. It’s fear, frustration, lack of confidence, poor socialization, or just straight-up bad genetics. Cutting the testicles doesn’t fix any of those.
In fact, some of the bigger recent studies actually show neutered dogs scoring higher on certain aggression and fear measures. So if your dog is already reactive or aggressive, don’t expect surgery to be the magic bullet. Fix the training and the management first. Neutering is a separate conversation.
Will it stop male dogs from lifting their leg?
Sometimes. Not always.
Marking is heavily influenced by testosterone, so neutering reduces it in a good percentage of dogs — estimates I’ve seen range from about 50% to 80% improvement depending on the study. The key is timing. If you neuter before the habit is fully locked in, you have a much better shot. Once a dog has been lifting his leg on every mailbox, tree, and corner for a year or two, that behavior is often learned and can stick around even after the hormones are gone.
Will it stop humping behaviors?
Again — sometimes, not always.
Hormone-driven mounting drops in a decent number of dogs after neutering (roughly half to two-thirds in the studies). But humping isn’t only about sex. Dogs hump when they’re excited, stressed, overstimulated, trying to settle themselves, or just because it feels good and they’ve practiced it a hundred times. Once it becomes a habit or a self-soothing behavior, the surgery often doesn’t touch it.
I’ve seen plenty of neutered males (and even some spayed females) still go to town on pillows, other dogs, or people’s legs. If the behavior is already established, train it out the same way you’d train any other unwanted behavior. Don’t pin all your hopes on the scalpel.
Bottom line from my side of the fence
If you’re not breeding and you don’t have a working dog, yes — I think most pet dogs should eventually be neutered or spayed. Just wait until they’re done growing (around 18 months for most breeds, later for the really big ones). That timing gives you the best shot at avoiding the joint and cancer risks the research keeps highlighting, while still getting the practical benefits of no heat cycles, lower marking drive, and reduced chance of accidental litters.
Everything else — learning ability, aggression, leg lifting, humping — is secondary. Training and management will always matter more than whether the dog still has their original equipment.
That’s my two cents after 1400+ dogs. Your dog, your call. Just make it an informed one.