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Why and When Should you Desex your Dog

It certainly was a question we never pondered for any of our dogs. 

Our Tervueren Conner was desexed before he reached 6 months of age 12 years ago simply because that's what our vet recommended and we would save on council registration fees. Our two rescue Malinois joined our family aged 9 months and 26 months respectively and had already been desexed by the rescue shelter.

Yet, this topic appears to b
e controversial in some circles of late so we sought the expert advice of Veterinarian Dr. Joanna Paul from Creature Clinic and Vet Behaviourist Dr. Katherine Macmillan from Croydon Pet Hospital to review the pros and cons from both a medical and dog behaviour perspective, based on the latest research.

What are the main reasons why a dog should be desexed?

There are many important reasons for desexing our pets. From a community point of view, desexing your dog will prevent any accidental litter of puppies


Around 44,000 dogs are euthanased in Australia by shelters and pounds in a year [1]. This is a staggering number and a very strong reason on its own to desex all pets!

Additional reasons to consider desexing your dog include:


  • It prevents unwanted behaviours. These are behaviours that are very normal for in intact dog, and include urine marking, humping and masturbation. 
  • Desexed dogs are likely to be more focused on their owner, instead of being distracted by nearby bitches on heat etc. 
  • Desexing removes the temptation to escape the property to search for a mate when in season (females) or if they smell a female in season (males). 
  • Entire females will drip blood around the house during part of their cycle. 
  • If you’re still wavering, there are of course the many health benefits!

What are the benefits of desexing your dogs? 

For a huge array of reasons, desexed dogs generally live longer than their entire counterparts. Some of the health benefits of desexing include:

1) Prevention of dystocia. Dystocia is difficulty during labour and can result in death of the dam or puppies or requirement for an expensive an invasive caesarean section. 

2) Prevention of other health problems associated with breeding such as Milk Fever

3) Prevention of pyometra, which is an infection in the uterus. Pyometra is deadly and while surgery can be life-saving, it is a complex and difficult procedure and can be very expensive.

4) Prevention of testicular tumours.

5) Reduced risk of prostatitis.

6) Reduced risk of perineal hernias.

7) Reduced incidence of perianal adenomas.


8) Reduced risk of mammary (breast) cancer. Importantly, the risk is most reduced if a female is desexed before her first season, and increases with each season. Desexing after several seasons is unlikely to be of benefit in reducing the risk of mammary tumours.

9) Prevention of hormone-associated alopecia (hair loss).

However no balanced discussion on pet desexing would be complete without including the potential drawbacks, and there certainly are some.

What are the potential negative effects of desexing your dog?

The negative health effects of desexing can include:

1) Increased risk of some tumours (notably osteosarcoma in large breeds)

2) Increased risk of cruciate disease – particularly when desexing is done early.

3) It can lead to hormone-responsive incontinence in females

4) It can be associated with weight gain (and hence conditions associated with high body weight like pancreatitis).

Are there any legitimate medical reasons why a dog shouldn't be desexed?

There are really no medical reasons to avoid desexing.

Anaesthesia is very safe for the vast majority of dogs. Some dogs have bleeding disorders (e.g. Von Willebrand’s Disease) and for these dogs precautions can be taken to ensure there are no complications from the procedure.

Will desexing change your dog's behaviour? 

Yes, desexing might change your dog’s behaviour.

Often there is a reduction in sexual behaviours, although dogs can hump legs for other reasons such as anxiety, and the same is true for urine marking. 

The effects of desexing on aggression are variable, and different studies have conflicting findingsWhile increased testosterone is sometimes associated with aggression, reducing the testosterone can actually lead to reduced confidence. A dog with reduced confidence may also be more aggressive!

Desexing does decrease the aggression that is seen specifically between entire male dogs. Some entire females can develop aggression or show an increase in aggression when they are in season. This does not always reduce back to baseline when oestrus passes. 

Overall, the effect of desexing on behaviour probably depends on the individual so unfortunately it’s not something we can predict with any accuracy.

What is the best age to desex or neuter a dog?

There is no one particular age that is ‘best’. There are pros and cons to different options.

The advantages to desexing before sexual maturity (so around 6 months of age) include:

  • Reduced risk of mammary tumours 
  • Less complicated surgery and less expensive surgery 
  • Likely lower council rates for registering your dog 
  • Reduced chance for sexual behaviours to become established 
  • Reduced chance of accidental breeding 

Some disadvantages to desexing when young include:
  • Increased risk or joint problems later in life 
  • Increased likelihood and severity of hormone-responsive incontinence. 
  • Increased anaesthetic risk (only if very young) 

There are advantages to desexing when older (generally when dogs are skeletally mature which is between 12 and 24 months depending on the breed). They include:
  • Reduced risk of joint disease later in life 
  • Reduced risk of some tumours 
Disadvantages to desexing when older include:
  • Surgery is more difficult with longer recovery time and increased cost. 
  • Some undesirable sexual behaviours may have become established. 
  • Greater chance of accidental litters. 
In general, the bigger the dog, the greater the advantage of leaving desexing until later

Are there any viable alternatives to surgical desexing?



There are hormonal implants available for male dogs called Suprelorin (Virbac) and these will last either 6 months or 12 months. 

These can be costly, and there is a potential for some dogs to become permanently infertile so they are not recommended for dogs that are intended to be bred from.

Side effects include the occasional mild swelling at the implant site which resolves naturally, and it is not recommended for dogs that have not yet reached puberty.

What myths would you like to dispel?

Myth #1 - D
esexing is a solution to Aggression 

This is only very rarely the case (see above). While temperament is inherited and it is a good idea not to breed from dogs with behavioural problems, desexing will not fix the issues. The underlying cause of the aggression needs to be identified and the problem managed. 

Myth #2 - D
esexing is promoted by vets because they want to make money

This is simply not true. There is much more money to be made doing complicated pyometra surgeries and caesarians than routine desexing. If vets wanted to make the most money from your pet they would strongly suggest NOT desexing and NOT vaccinating. 

Myth #3 - A
ll female dogs should have a litter before being desexed 

Bitches that are to be bred from, need to be selected carefully for having particularly good physical attributes and temperament. Breeding a dog with congenital faults or with a behavioural problem will only contribute to more unwanted dogs being euthanased. 

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5532565/
 Published online 12/07/17

written for Australian Dog Lover, August 2018 (all rights reserved).

About Dr. Joanna Paul


Dr Joanna Paul is a Melbourne-based veterinarian who has been working in partnership with pet parents to care for their furry kids for over a decade.

As well as work, she divides her time between her gorgeous dog Billy, a menagerie of other furkids, three children and her own website Creature Clinic for pet parents.



About Dr. Katherine Macmillan

Kathy graduated from the University of Melbourne in 2001 with honours. She also has additional qualifications in Veterinary Behavioural Medicine (obtaining her memberships of the Australian and New Zealand College of Veterinary Scientists in 2010). Kathy is also DAFF-accredited for companion animal export so can help with testing and treatments if you are planning to move overseas with your pet.

When she is not working at Croydon Pet Hospital she can be found running in the bush somewhere. She regularly competes in ultra-marathons (races over 42km), usually on trails. Generally the hillier the race the better!

Kathy lives with a seven year old Kelpie, Rikki, who used to be her running companion but has recently started complaining that she runs too far. Kathy is also mum to 5 chooks and a part Arab gelding called Monty, who is generally a paddock ornament but occasionally gets taken out for a stroll in the bush.
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