Does Neutering Calm a Dog Down?

Anyone who has taken a puppy to the vet in the last thirty years has heard more or less the same thing: “have him neutered, he’ll calm down“.

It has become almost automatic, repeated so often that it seems like an established fact. A scientific review published in 2026 in Animal Reproduction calls all of this into question.

The authors combed through decades of research on the subject and reached an uncomfortable conclusion: there is not enough solid evidence to justify spaying or neutering with the sole aim of changing a dog’s behaviour.

What did the study actually find?

The striking finding is that some of the studies included in the review recorded the opposite of the expected effect: after surgery, some dogs showed more fear, more anxiety and, in some cases, more pronounced aggression.

Not all of them, and not always, but enough to make the idea of a rule that applies to every dog untenable.

The reason has to do with something that is often forgotten: reproductive hormones don’t only deal with reproduction.

Testosterone, oestrogen and progesterone are also involved in how the brain works, in learning, memory and stress management. It’s a mechanism closely linked to the way a mother’s hormonal stress affects her puppies’ brains even before they are born.

Removing them surgically is not a behaviourally neutral operation: it is a change that has knock-on effects on the nervous system, and every dog processes it in its own way, depending on genetics, age, sex, breed and temperament.

A lesser-known side effect of spaying, linked precisely to these post-operative hormonal imbalances, is false pregnancy (pseudopregnancy), which can appear in the weeks after the operation if it is carried out at the wrong point in the cycle.

Alternatives that preserve hormones

The most interesting part of the review concerns two procedures that are still uncommon, in Italy and in many other countries, which prevent reproduction without switching off the body’s hormone production.

Vasectomy

In males, a vasectomy stops sperm from passing through but leaves the testicles intact.

The dog can no longer father puppies, but it keeps producing testosterone just as before the operation. The hormonal and character differences between males and females already weigh heavily when choosing a puppy, and they are worth bearing in mind when considering this procedure too.

Ovary-sparing spay

In females, this technique removes the uterus but leaves one or both ovaries in place. No pregnancies, but ovarian hormone production stays active.

The authors of the review don’t claim that these techniques are better across the board.

What they say is that they deserve more attention than they get today, because they may preserve some of the benefits associated with natural hormones while still keeping reproduction under control.

The risk of pyometra: why it should be kept separate from the behaviour question

There is one point that deserves to be singled out, because otherwise things get confusing: pyometra.

Pyometra is a serious, often life-threatening uterine infection that affects entire (unspayed) females, especially as they get older, usually in the weeks after a season.

It is one of the most solid health reasons, probably the most solid, why many vets recommend traditional spaying in bitches, and it is a real risk, not a theoretical one: the cumulative lifetime incidence in an entire bitch is far from negligible.

Here the Animal Reproduction review leaves no room for doubt: removing the uterus eliminates the risk of pyometra, whether or not the ovaries are left in place.

This is why an ovary-sparing spay is not a “halfway” compromise on the health front: the organ that becomes infected is removed anyway.

The only difference compared with a traditional spay is that hormone production continues, not the protection against pyometra.

Vasectomy is a different matter, because it concerns males and has no bearing at all on the risk of pyometra in females: the two procedures are not equivalent and meet different needs depending on the dog’s sex.

So, to neuter or not?

The review doesn’t take a position either way. It doesn’t say that dogs should be spayed or neutered, nor the opposite.

The message is a different one: enough of the “one size fits all” approach. Every decision should be made by looking at the individual dog, its health, lifestyle, the behaviour it has already shown and its real reproductive risk, together with your vet, also taking into account all the health factors that come into play in the long term, not just behavioural ones.

For anyone who breeds or lives with a Labrador, this means one practical thing: before deciding whether and when to neuter, it’s worth making a tailored assessment rather than following a standard protocol applied regardless.

Questions and answers

Does neutering reduce aggression in dogs?

Not automatically. The review found cases where aggression increased after surgery rather than decreased. The effect varies from dog to dog.

At what age should a dog be neutered?

There is no age that suits every dog. The choice depends on breed, size, health and goals (reproductive, behavioural, health-related), and should be discussed case by case with your vet.

Is vasectomy widely available?

It is still much less common than traditional castration. Not all vets offer it: it’s best to ask your own practice directly.

Does spaying help prevent disease?

Yes, in part. The clearest case is pyometra: a traditional spay, by removing the uterus, eliminates this risk in bitches.

An ovary-sparing spay offers the same protection, because the uterus is removed in this case too.

On other fronts (some reproductive tumours, for example) the balance is less clear-cut: the review points out that hormones also have protective functions, so this should be assessed case by case with your vet.

If the ovaries are left in, can my bitch still get pyometra?

No. Pyometra is an infection of the uterus: if the uterus is removed, as happens in both a traditional spay and an ovary-sparing spay, the risk drops to zero.

The ovaries left in place have nothing to do with this particular disease.

What changes with an ovary-sparing spay?

Pregnancy is prevented by removing the uterus, but the bitch continues to produce ovarian hormones, and the season may still show outwardly (with no risk of pregnancy).

Not sure whether or when to neuter your Labrador? The MyLabrador’s team can help you weigh up the best choice for your dog, based on its health, age and risk of pyometra. Contact us for personalised advice.