When to neuter a dog? What age is best


Just this past weekend I was asked by a friend “when is the best time to neuter my dog?” In the past, I would have quickly replied “oh around 6-9 mths old would be best”, but now, with studies looking at the relationship between neutering and health of our dogs, that advice may well be regarded as obsolete.

Just quickly, when we talk about a neutered dog we are referring to a male dog that has had his testicles removed. In some countries, this may also be referred to as castration.

In contrast, spaying a dog is the process of removing a bitch’s ovaries and uterus so that she is unable to have puppies.

Back to the question:

There really is no one size fits all answer to the question of when you should neuter your dog. Evidence-based medicine suggests that there is a complexity to the different guidelines for age of neutering depending on the breed of dog and it’s behaviour.

Many of the studies relating to timing of desexing are retrospective – meaning that they are assessing data from the past. We also don’t know important facts like behaviour, vaccination status, weight, and age of desexing.

The vast majority of these studies show conflicting data making assessment of the studies difficult and recommendations for timing of desexing impossible. Honestly, the statistics make my head hurt and much of the information on the net has not interpreted the findings accurately.

One important fact to remember is that our pets are living longer lives, just like us. We do know that desexing does increase lifespan and as a result, the risk of developing conditions like cancer may be higher (1) and have little relevance to desexing.

We therefore need to ask – Are these study results due to the dog being sterilised? Or is it just a function of getting old? Further prospective studies are required to answer this question. (One study in Golden retrievers is currently being undertaken).

What factors do I need to consider before neutering my dog

When deciding the best time to neuter your dog, it’s important to consider the following:

  • Breed size i.e. giant breed vs small breed
  • The behaviour of your dog – is he showing signs of aggression vs anxiousness
  • Cancer risks
  • Your ability to keep your dog from roaming and subsequent consequences i.e. injury, unwanted matings

Neutering large or giant breed dogs

Neutering prior to puberty (<6 months) results in the removal of hormone influence on physeal growth plates resulting in delayed closure. This leads to an increase in bone length (your dog may grow very tall) and can lead to joint problems for some dogs. (2)

The risk of developing hip dysplasia and cranial cruciate disease may also increase with pre-puberty desexing(3). Again, we need to remember that genetics and exercise do play a large role in the development of these conditions.

The effect of neutering on dog behaviour

A very important consideration when deciding when to neuter your dog is what their behaviour is like. This is even more important with our large or giant breeds.

Anxious and aggressive behaviour from these breeds can be disastrous in our society(4).

Again, there is no easy or correct answer and as much as I hate to say “it all depends”!

One thing we are sure about is that once an intact dog is displaying aggressive behaviour, neutering will unlikely result in any change in that behaviour (5).

In summary, the effects of neutering on dog behaviour require more study as the majority of the studies are producing conflicting results.

effect of spaying and neutering on relative risk of disease in dogsThe risk of cancer in a neutered dog

Again, the evidence is still variable for this topic.

Removing the testicles will prevent testicular cancer and any other cancers that rely on testosterone to grow.

There are some other cancers that may be more likely in the castrated dog, but the evidence is lacking. Is this due to age because we know castration results in a longer life-span?

Ownership responsibilities

The most important question to ask yourself is

“are you able to keep your dog confined so that they are unable to escape?”

We have a huge problem with unwanted and stray dogs. If your property is not fenced, if you want to let your dog roam and be ‘off leash’ then you need to have your dog neutered sooner rather than later.

What are the benefits of neutering your male dog?

  1. You will prevent unwanted pregnancy and lower the risk of over-population.
  2. Your dog will roam less – and this means less risk of accidents such as being hit by a car or getting into fights with other dogs. Let’s also not forget that a roaming dog may end up in your local Pound resulting in a fine to regain possession.
  3. There will be less marking of territory – again this is very dependent on the timing of neutering. If neutered prior to development of sexual characteristics then marking won’t occur. Once marking of territory starts, it is unlikely to stop.
  4. Will prevent testicular cancer and can decrease risk of prostate problems such as prostatitis (inflammation/infection) and benign prostatic hyperplasia (enlargement) that are due to hormones.
  5. Will prevent some types of hernias and tumours of the anus.
  6. Large breed male dogs after they hit puberty can be very strong, aggressive and very difficult to control. You need to be very sure of your ability to control and socialise these dogs appropriately.

Dr Leigh’s two cents on when to neuter a dog

My personal bias on this topic is that we still have a lot to learn and we need to make our decisions based on the individual animal andwhen to neuter a dog what age is best the family it lives in.

For the vast majority of smaller dogs, I am happy for them to be neutered at 6 to 9 months of age or prior to puberty if in a shelter situation.

Large or giant breeds, it may be more appropriate to delay neutering, however consideration needs to be given regarding behaviour and ability of the owner to care for these dogs.

Let’s also not forget that patient genetics and the environment play a huge and often forgotten role in the development of many of these disease and behavioural processes.

Bottom line, it is best to talk with your vet or with one of our online vets about your individual situation. There are no hard and fast rules and together with your vet we can determine the best option for your dog.

  1. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0061082
  2. https://www.ncbi.nlm.nih.gov/pubmed/2045340
  3. https://www.ncbi.nlm.nih.gov/pubmed/18598150
  4. https://www.rspca.org.au/sites/default/files/RSPCA%20Australia%20Annual%20Statistics%20final%202016-2017.pdf
  5. https://www.frontiersin.org/articles/10.3389/fvets.2018.00018/full