Animal Happiness Vet

Updates in the desexing debate

Updates in the desexing debate

Updates in the desexing debate

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Should I sterilise my pet? If so, when?

We’ve known for a while now that there are a bunch of benign and some down-right nasty things that can affect our pets if we don’t sterilise them3. There is also a whole bunch of more old-school style wisdom regarding a range of possible benefits to leaving your pets unsterilised. So where does the truth lie, and has any more recent research shed light on this?

This post examines some fascinating new research that will surprise many out there.

No seriously, should I sterilise my pet?

Spoiler alert: the answer is still yes. There is no doubt that sterilised dogs and cats live longer on average. They are no longer driven by sexual desires they have no outlet for, they carry no risk of suddenly presenting with a growing belly, and they grow old much more gracefully. No male dog has ever felt “less of a man” as a result of castration, because no dog ever feels “like a man” – these are our views projected onto them. Their lives are far simpler, and far purer.

So it needs to be done at some stage – but when is the best time?

This is where the scientific evidence is getting more interesting. The studies out there vary quite wildly, and many of them have numbers too low to provide much statistical credibility, but the picture is developing! The largest study to date1 investigated the clinical records of 759 golden retrievers and compared the rates of various diseases in early sterilised and non-sterilised dogs. Goldies were chosen because of a high breed incidence of various cancers and various joint problems. The results showed that for several of the less common cancers, as well as cruciate ligament injury and hip dysplasia, early sterilisation increased the risk of disease!

The effect of sterilisation on the incidence of mammary tumours has been known for a longer period of time2 and is summarised here:

Reproductive Status at Time of sterilisation Mammary Tumor Risk
Never in estrus 0.5%
In estrus 1 time only 8%
In estrus ≥2 times , regardless of age

and ≤2.5 years of age

and >2.5 years of age




Clearly this study shows a dramatic benefit in early desexing. But what else is affected? A range of tumours have been shown to occur with a higher incidence in dogs sterilised before 12 months of age. As noted above, much of this information relates purely to golden retrievers and may not be applicable to other breeds. However, there is a general sway of evidence that suggests remaining intact for at least the first year provides some tangible benefits to male and female dogs:

Condition Effect of spaying on Relative Risk Effect of Castration on Relative Risk
Overall longevity Mild increase in longevity Mild increase in longevity
Obesity Moderate increase Moderate increase
Cranial cruciate ligament disease Moderate increase* Moderate increase*
Hip dysplasia Mild increase* Mild increase*
Mammary tumors Marked decrease* N/A
Uterine, ovarian, vaginal tumors Prevents N/A
Testicular tumors N/A Prevents
Perianal gland tumors N/A Marked decrease
Prostatic carcinoma N/A Mild increase
Lymphoma Mild increase Mild increase*
Mast cell tumors Mild increase N/A
Hemangiosarcoma Mild increase* Mild increase
Osteosarcoma Mild increase* Mild increase*
Transitional cell carcinoma Mild increase Mild increase
Urinary sphincter mechanism incompetence Moderate increase* N/A
Cystitis Mild increase* N/A
Benign prostatic hyperplasia N/A Marked decrease
Perineal hernia N/A Moderate decrease

*Age at time of surgery may be important.

Ok, so that all mostly confused me. What does it mean?

The upshot of all of this is that there really is no right answer. There is no perfect time to sterilise your pet. There are good arguments not to sterilise very early and there and really good arguments not to leave it too late. For me the outer bounds are clear –

  • 3 months, as some welfare organisations and breeders insist on, is far too early
  • 6 months, as I used to recommend, is also too early in many situations
  • 7 years plus is too late
  • A male dog who is starting to develop troublesome “boy” behaviours such as peeing on furniture or humping soft toys and children should be sterilised long before these behaviours become habituated. A male dog who has done this for more thana few months may never stop even if he is sterilised!
  • A female pet (of any species) who appears to have health problems associated with coming into season should be sterilised without delay at any age

In the more straight-forward situations with average healthy pets I feel that sterilising your pets should be done sometime between 1 and 2 years of age. I recommend earlier for smaller animals and for any showing problems (as noted above), and later for larger dogs.

Please feel free to add your comments below. When was your pet desexed? Do you now think it was too early or too late?

  1. de la Riva et al. Neutering Dogs: Effects on Joint Disorders and Cancers in Golden Retrievers. 2013,
  2. Schneider et al. Factors Influencing Canine Mammary Cancer Development and Postsurgical Survival. 1969,
  3. Fossum et al. Small Animal Surgery. 2013, Elsevier

10 thoughts on “Updates in the desexing debate

  1. Brooke

    As a breeder of Dogue de Bordeaux, we sterilise our puppies by way of vasectomy for dogs and ovarian sparing Spey for bitches. This allows the sex hormones to play their role in overall development. To date (have been doing this for the last 5 years) our puppies have gone on to grow into normal healthy adults. As we also hip/elbow score all our dogs (including those in pet homes), our findings have been interesting and we will continue to study our lines in this way. We recommend to our pet buyers to desex (castrate) between 1.5-5yrs. It will be interesting to look back on in the future, the difference diet, excersise, desexing status make for overall health 🙂

  2. danl

    I dont think animals should be spayed or neutered, they should live as they would live natural lives. If you’re getting and bringing an animal in your life, they should bring the whole animal with them. Why deny one part of there life , one part from them? If you accept an animal, accept them with all that they come with, and not deny one part of there there existence.

    1. Dr Gary Beilby Post author

      It is important to note here Danl, that sterilisation is known to be so important in the prevention of unwanted litters of cats and dogs that many local governments in Australia require pets to be sterilised by law. So for many it is very much a question of when, not if.
      From my perspective – as a vet who treats behavioural problems regularly in dogs and cats – it is also so very important for the mental wellbeing of an animal. For a dog or cat to remain unsterilised means it is saddled with sexual desire it simply cannot fulfill. This is a recipe for sadness and frustration that a pet shouldn’t be made to endure.

  3. Rosie Beckett

    I am thinking of desexing my dog and I am glad that you shared the benefits because I did not realize that it can help my dog to live a longer life! The fact that my dog will age more gracefully and will be more likely to avoid sicknesses like tumors is a huge benefit. Also, the fact that I won’t have to worry about my dog getting pregnant will give me peace of mind because I can only handle one dog!

  4. Dean Phillips

    I thought it was really interesting how you said that there isn’t a doubt that desexed dogs and cats live longer on average than those who have not been. My brother and his wife recently rescued a kitten from the local animal shelter and they have been trying to find a place that can desex him for them. It seems like it would be beneficial for them and for the cat to find a professional who can properly perform the procedure for them.

    1. Dr Gary Beilby Post author

      Well, not just beneficial Dean. It would actually be breaking several laws for someone to try and perform this procedure if they were not a professional veterinarian!
      Further, male cats rapidly become an urban nightmare if they are left unsterilised, and in most parts of the country it is illegal these days to own a cat that hasn’t been sterilised unless you are a registered cat breeder.

  5. Deborah Leitch

    My daughter got a female Rottweiler pup 2 years ago and after lots of reading and investigating I was pleased to see your comments as a vet looking into the pros and cons of desexing/castrating.
    As with any living being/animal if we take away the bodies ability to use its hormones to grow it causes health issues. One of the things I read which I found interesting is that in large dogs certain bones finish developing at different stages and if we take away the hormones needed to fully develop the dogs bones this can cause hip dysplacsia and other structural issues. I recommended my daughter to get her dog desexed at around 2 years of age as bigger dogs can take that long to fully developed. Her vet kept pushing for an earlier desexing but she held out till about 16 months. I would love to see the procedure of vasectomy and hysterectomy done so that the hormones are still there to help grow and develop the animals but stop the unwanted pregnancies.

  6. Words Animals

    Your article is very helpful for me after reading your article I got a lot of information my name is Elias Jaxon. I am gating information about cat your article is very fantastic.

    1. Dr Gary Beilby Post author

      No problem Victoria. However, I would add, you don’t need to look for a clinic that specialises in desexing as it is the most common procedure every veterinary practice does – Therefore we are all specialists in that!

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