Updated November 27, 2020
I’m going to lead you through the evidence we have for the age to desex a dog. I’m not going to give you the ‘right’ answer, but instead the tools so you can make the best decision for your dog. With the new mandatory 6-month desexing in Adelaide, this is the evidence you may need to ask your vet for a postponement.
Firstly, let’s establish the reasons why we desex male and female dogs. Here’s the evidence we have in favour of neutering.
Why Desex Male Dogs
- Lifespan is increased
- Aggression between dogs and aggression towards family members are reduced (read here for a full discussion of the effects of desexing on aggression)
- Urine marking and roaming are reduced
- Medical conditions such as prostatic enlargement, cystine bladder stones, perineal hernia, testicular tumour & perianal tumour are reduced or eliminated.
Why Desex Female Dogs
- Lifespan is significantly increased
- Heat periods and unwanted pregnancy are eliminated
- Pyometra (uterine infection) is prevented
To help dog owners I tell them:
Desex males for behaviour; Desex females for health. References can be found below.
Why NOT Desex A Dog?
Apart from infertility, proven negatives associated with desexing include:
- Increased risk of dogs being overweight or obese
- Higher incidence of hip dysplasia and cruciate ligament problems
- Increased rate of certain cancers such as lymphosarcoma, haemangiosarcoma, mast cell tumour
- Prostate and bladder cancer are more common in males
- Urinary incontinence is more common in females
Although they sound scary, we shouldn’t be overly concerned about the cancers associated with desexing. That’s because there’s clearly a trade-off in lower rates of other diseases: neutering gives a moderate increase in lifespan to both sexes of 9 to 12 months. In other words, although some causes of death become more common, other causes of death must become less common.
I’m much more concerned about accidentally increasing the rate of debilitating non-life-threatening diseases. That’s the information I use to decide when to desex.
Best Desexing Age: 39 Dog Breeds
The following data come from two 2020 studies of purebreeds and mixed breeds of different sizes. They looked at the rate of joint problems, cancers, and urinary incontinence at different desexing ages.
In this chart I have chosen a time for neutering that reduces any problems found for each breed. When possible, I have matched it to our general advice below. You can read the raw data and my reasoning by following the links.
Take away messages:
- small breeds suffer few or no known problems
- many medium-sized and large breeds benefit from a modest delay
- giant breeds do not appear to need later desexing
|Dog Breed||Male Desexing Age||Female Desexing Age|
|Australian Cattle Dog||9 months||9 months|
|Australian Shepherd||9 months||9 months|
|Beagle||9 months||9 months|
|Bernese Mountain Dog||2 years||1 year|
|Border Collie||1 year||1 year|
|Boston Terrier||6 months||6 months|
|Boxer||9 months||9 months|
|Bulldog||6 months||6 months|
|Cavalier King Charles Spaniel||6 months||6 months|
|Cavoodle sized dogs||6 months||6 months|
|Chihuahua||6 months||6 months|
|Cocker Spaniel||9 months||9 months|
|Collie||9 months||9 months|
|Corgi||9 months||9 months|
|Dachshund||1 year||1 year|
|Doberman||9 months||2 years*|
|English Springer Spaniel||9 months||2 years*|
|German Shepherd||1 year||1 year|
|Golden Retriever||1 year||1 year|
|Great Dane||9 months||9 months|
|Irish Wolfhound||9 months||9 months|
|Jack Russell Terrier||6 months||6 months|
|Kelpie sized dogs||9 months||9 months|
|Labrador||6 months||1 year|
|Large breeds (other)||1 year||1 year|
|Maltese||6 Months||6 months|
|Miniature Schnauzer||6 months||6 months|
|Pomeranian||6 months||6 months|
|Toy Poodle||6 months||6 months|
|Miniature Poodle||1 year||6 months|
|Standard Poodle||9 months||9 months|
|Pug (view paper)||6 months||6 months|
|Rottweiler||1 year||1 year|
|St Bernard||9 months||9 months|
|Staffy sized dogs||1 year||1 year|
|Sheltie (view paper)||6 months||2 years*|
|Shi Tzu (view paper)||6 months||6 months|
|West Highland White Terrier||6 months||1 year*|
|Yorkshire Terrier (view paper)||6 months||6 months|
Now also have a look at the chart featured at the beginning, in which I’ve summarised the results of three older studies from the University of California-Davis. Feel free to focus on the details but I’ll explain the main points later.
The Problem With The Evidence
From reading these studies it’s clear that early desexing increases the risk of joint diseases in certain dog breeds. The argument regarding cancers is less certain. The theory is that hormones influence normal development of joints in some breeds. Once a joint is fully grown, hormones shouldn’t make much of a difference. But there’s still a small problem: body weight.
Not one of these observational studies is controlled for weight. The desexed groups are almost certainly heavier, and we know that weight is a significant risk factor for cranial cruciate ligament disease (CCLD) and hip dysplasia (HD). This is a quote from one study:
…the occurrence of HD and CCL in early-neutered dogs is a combined function of the effect of neutering on growth plates, as well as the increase in weight on the joints brought on by neutering. Reference 1
This doesn’t change the findings, which are statistically significant for most of the large differences. However, the question remains: if an owner can control their desexed dog’s weight, is there still a risk of joint problems? Until this is answered (if ever!), it’s safest to follow these guidelines…
When To Desex A Dog
Apart from specific breed advice above, our general recommendations to all dog owners are below. Prices for the desexing options can be found here.
6 month desexing
The earlier age is still likely to be the best time for most smaller dog breeds. This avoids a heat period in females and pre-empts most behaviour change in males.
Neutering at 12 months is recommended for breeds prone to hip dysplasia and cruciate disease (though the newer data suggests that 6 months is OK for male Labradors and even giant breeds). Later desexing may also be helpful for females with urinary incontinence.
Females with a deeply recessed vulva should also be allowed to have a season to reduce the risk of perivulval dermatitis as adults. After a season in females, it’s best to wait at least 2 months for everything to settle down prior to surgery.
Early age desexing
Early age desexing is important for rescue shelters to avoid overpopulation but otherwise is best avoided. There have been very few good studies looking at 8 week desexing but in my opinion it’s likely that any effects on joints will be magnified by taking desexing even earlier. Read here about the risks of incontinence associated with early age desexing.
For dog owners wanting to preserve female hormones through life, Ovary Sparing Spay is another alternative. Follow the link to learn more or read about the choices available for dog desexing here.
Many owners of male dogs who opt for late desexing find problem behaviours develop that can be quite hard to manage. To these owners, we say: go as far as you can but don’t feel guilty to give up early. Bad habits can be very hard to stop once they start, and the evidence isn’t ironclad. Any delay should help.
When Desexing Exemptions Will Apply
Since July 2018, with compulsory 6-month desexing in South Australia, vets need to register a temporary exemption of some dogs until maturity. The period can be up to 18 months. It can be applied to any breed shown to be at higher risk of hip dysplasia or cruciate disease, not just the ones featured in these studies. This is speaking to the evidence in the safest way and it’s only right.
Just ask us if you want this done; it’s quick and easy. Note that to comply with SA law we will not provide permanent exemptions unless there are compelling health reasons.
In Australia, there is a strong push from society for all dogs to be desexed. I think an impartial reading of the pros and cons of desexing male dogs will lead most people to decide it’s also in their pet’s best interests. Female dogs, who get a comparatively greater lifespan advantage, present an even more compelling case. Although you are welcome to disagree, to me the only decision is when to do it.
References & more studies showing health effects of desexing can be found at our page on Desexing Male Dogs. The five studies quoted here are:
- de la Riva, G. T., Hart, B. L., Farver, T. B., Oberbauer, A. M., Messam, L. L. M., Willits, N., & Hart, L. A. (2013). Neutering dogs: effects on joint disorders and cancers in golden retrievers. PloS one, 8(2), e55937. Full Article.
- Hart, B. L., Hart, L. A., Thigpen, A. P., & Willits, N. H. (2014). Long-term health effects of neutering dogs: comparison of Labrador Retrievers with Golden Retrievers. PloS one, 9(7), e102241. Full Article
- Hart, B. L., Hart, L. A., Thigpen, A. P., & Willits, N. H. (2016). Neutering of German Shepherd Dogs: associated joint disorders, cancers and urinary incontinence. Veterinary Medicine and Science. Full Article
- Hart, B. L., Hart, L. A., Thigpen, A. P., & Willits, N. H. (2020). Assisting Decision-Making on Age of Neutering for 35 Breeds of Dogs: Associated Joint Disorders, Cancers, and Urinary Incontinence. Frontiers in Veterinary Science, 7, 388. Full Article
- Hart, B. L., Hart, L. A., Thigpen, A. P., & Willits, N. H. (2020). Assisting decision-making on age of neutering for mixed breed dogs of five weight categories: associated joint disorders and cancers. Frontiers in veterinary science, 7, 472. Full Article
By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. These blogs are from a series regularly posted on email and Twitter. Subscribe via email here to never miss a story!
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