Neutering in dogs: a health and behavioural debate

How can we help our clients make an informed decision?

12 December 2019, at 9:00am

Neutering is a complex topic for dog owners, made even more so by conflicting advice, advances in research and almost endless folklore of how it will affect dogs. To help owners to make an informed choice about what to do, we asked Carolyn Menteith, dog behaviourist and trainer, and Robin Hargreaves, director, veterinary surgeon and former BVA president, both members of the Agria Specialist Health Team, to discuss neutering and its impact on health and behaviour.

Dog health

Robin: When it comes to health, the two main reasons to neuter female dogs are the dramatic reduction in mammary cancer in animals neutered at a young enough age and the absolute prevention of the potentially fatal pyometra.

In male dogs, neutering can reduce the incidence of prostatic disease. While we see fewer cases of benign prostatic disease in neutered males, it isn’t so clear in prostatic cancer that neutering makes a difference. Compared with females, the health drivers for neutering males are not so strong.

Are there negatives for health in respect of neutering? Yes. Most insidiously across animals that have been neutered is the serious potential for weight gain – they simply find it easier to put weight on. And if this is not addressed it can complicate every other health problem as life goes on.

For females specifically, there is an increased incidence of urinary incontinence. While manageable in most cases, medication will probably be required forever. There also continues a debate on the timing of neutering and whether it is responsible for an increased rate of urinary incontinence in females. It appears that spaying after the first season can reduce this.

Neutering male dogs under the age of 12 months, or before the dog has reached skeletal maturity, is not advised. This is due to the increased length of time growth plates will take to fuse following a reduction in testosterone, creating a statistical increase in the incidence of injuries among animals that have been neutered at a younger age.

I suspect over the next five years we will see a lot more data and will have greater clarity over the ancillary risks and benefits. But at the moment with male dogs it’s a case-by-case decision, whereas for female dogs, with the health risks being so much more significant, I think we can be clear that a non-breeding female is better off spayed.

Dog behaviour

Carolyn: Looking at dog behaviour, thoughts are very much the same – it is a case-by-case decision. People used to think if you take testosterone away from male dogs they would be easier to live with, but that’s not always the case. Aggression can have its roots in fear or anxiety, so by taking away testosterone, which may be giving the dog some confidence, you could end up with a more fearful dog, that in turn becomes more aggressive. There is also evidence of similar results in female dogs. In the same way, there can be an increase in other phobias and touch sensitivities as well – so neutering to improve behaviour isn’t as clear cut as we previously thought.

It’s true that it will prevent or reduce most sexually driven behaviours, such as running off after a bitch in season or excessive territory marking, and it may prevent some dog-to-dog aggression and male competitiveness – but it isn’t the panacea that people always thought it was to calm dogs down; in fact, there are some studies that show increased excitability in neutered dogs. We’re simply finding out more and more all the time about how hormones affect our dogs and about what happens when you alter that hormone balance. Where population control is not an issue, owners should talk to their vets – and if they are hoping to improve behaviour, their behaviourist – and make their decision on a case-by-case basis based on what is right for them and their dog.


Robin: We wouldn’t just book male dogs in to be neutered these days, there’s always a discussion about why. In the significant minority of cases, we realise that client expectations are completely awry and we would be disappointing people enormously if we carried out the operation.

With females, we’re confident that it’s the right course of action but it’s still important that people realise what the downsides might be: the potential for weight gain, for example.

The only certainty with neutering is that that animal will have no further part in the breeding process. Any other changes cannot be guaranteed, so it’s a risk–benefit analysis.

To find out more about how your practice could benefit from working with Agria and offering your clients five weeks of free insurance, get in touch with the Agria Vet Team by calling 03330 30 83 90