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Should I neuter my dog?

Neutering is the removal of an animal's reproductive organs, with the obvious results being that the dog is no longer able to reproduce. Neutering dogs is pretty common in this country and tends to be something that most owners view as routine. However, there are a lot of myths surrounding neutering which often results in people neutering their dogs for the wrong reasons and at the wrong time.

We are often asked by clients if and when they should neuter their dog, and so we thought it would be a good idea to delve a little deeper into this in order to help owners make informed decisions on whether or not to neuter their dog. First of all, this article will analyse some common reasons for neutering, and we will then go on to address when to neuter your dog if you have decided that this is the right thing to do.

Neutering prevents unwanted litters

It goes without saying that neutered dogs can't make babies, therefore preventing unwanted litters, which is a very valid reason for neutering your dog. There are plenty of unwanted dogs already and we don't want to add to this population accidentally. This is a particularly valuable strategy in countries where there are a lot of free-roaming or stray dogs or in multi-dog households. However, in most cases proper training, control and management is also enough to prevent your dog from mating.

This is particularly the case for males rather than females. If you are unable to recall your unneutered male from all distractions, you risk them running over to a bitch in heat and mating with them. Therefore it is important to have a high level of control and training, and neutering is not a replacement for this! There are however some cases where unneutered males have such a strong desire to reproduce that they are incredibly frustrated and constantly seeking out females, and in these cases it is often kinder to the dog to neuter them. This is a factor that I took into account when deciding whether to neuter Harley. He is very unbothered by females in season and whilst I would never leave him unsupervised with one, he can be off lead around them with no issues at all. This is partly due to the fact that he has a high level of training, and also because he is not particularly driven by his hormones.

Females can only get pregnant when they are in season. This tends to happen every 6 months or so, and usually lasts between 2 - 3 weeks. During this time, it is sensible to keep them separate from any unneutered males in the household, particularly when unsupervised, in order to prevent an accidental mating. When out and about, females generally won't go out of their way to seek out unneutered males, but it is important to be conscious that others might not have the same control over their dogs, and so many people keep their females on the lead or walk in less busy areas.

Neutering a dog calms it down and eradicate behaviours such as humping and marking

So many people believe that neutering their dog will calm it down and solve problem behaviours, but in most cases this is not true. Neutering a dog is only likely to solve these issues IF their hormones are the cause of these behaviours. It will have no effect if the behaviour has another cause.

For example, whilst humping could be a result of hormones, it can also be a result of overarousal and excitement. After all, there are plenty of neutered dogs that hump things that they shouldn't, and it is not just something that males do, females do too! Therefore, neutering your dog is unlikely to have any impact because the removal of their reproductive organs and associated hormones will not have any impact on their emotional state. Similarly, whilst marking can be fuelled by an unneutered dog's needs to mark their territory, it can also be a learnt behaviour and neutered dogs can mark just as much as unneutered dogs.

Unneutered males are more aggressive than neutered males

Unneutered male dogs can be more likely to show aggression towards other dogs (more often other intact males) as a result of the need to establish their hierarchy. Again, this comes from a natural instinct to find food, mates and territory, and other dogs can be perceived as a threat to this. A dog that acts in this way is often called a "dominant" dog.

However, as with other problem behaviours, neutering will only solve this issue if the aggression or reactivity is caused by the dog's hormones and the need to compete. An unneutered dog that is fighting other dogs out of insecurity will not benefit from being castrated, nor will a dog with a genetic propensity towards dog aggression.

In addition, some dogs are naturally very confident as a result of their personality, and neutering them will not change this. Take Odin for example, he is neutered but he is top of the hierarchy of our team dogs despite the fact that Harley is unneutered. Harley is lower down because, whilst he is still intact, he is not the most confident of dogs and does a lot better taking direction from other dogs rather than making the decisions himself. Similarly, some of Harley's best friends are intact males, and so it is possible for unneutered males to exist without issues.

On the flipside, neutering a dog can even make them insecure, particularly where they are already underconfident. Testosterone is linked to higher confidence, and so we don't want to limit an already insecure dog who needs all the help they can get! Therefore, even if neutering is your end goal for other reasons, it is important to work on your dog's confidence beforehand through training if you want to ensure that neutering doesn't have a negative impact.

Neutering my dog has health benefits

There are generally more health benefits associated with neutering female dogs than there are male dogs. Pyometra is a life-threatening illness in females, and it is caused by hormonal changes in the womb following the dog's season when progesterone levels are higher. This causes the uterine lining to thicken and if pregnancy doesn't occur over several seasons then cysts can form which secrete fluid and allow bacteria to grow. This is more common in older dogs and often requires surgery to remove the uterus, which can be a more complex procedure than a normal spay operation. Pyometra is fairly common, with studies showing that it affects around 25% of female dogs before the age of 10(1). Even where female dogs are used for breeding, breeders/owners often spay their dogs after they have retired them due to the risk of pyometra.

Spaying also prevents false pregnancies (also known as phantom pregnancies or pseudopregnancy), which is where hormonal changes following a season trick the body into thinking that it is pregnant and about to give birth. This can cause behavioural changes such as restlessness, lack of appetite, increased anxiousness and irritability. Spaying prevents these hormonal changes and eliminates the chance of a phantom pregnancy altogether.

The main health benefit of neutering male dogs is that it prevents testicular cancer. Testicular tumours are the third most common tumours in dogs, after cutaneous and mammary tumours, and are more common in dogs over the age of 10 years old (2). Studies have shown that some breeds are more prone to getting them, and so there is also likely to be a genetic component. The main risk of testicular tumours is obviously that they become cancerous. I have been unable to find any studies on the percentage of testicular tumours that become cancerous, but Blue Pearl Vet Hospital states that tumours of normal descended, or scrotal, testicles are usually benign while tumours of undescended testicles are much more likely to be malignant(3). Therefore, it would appear that neutering is much more important if your dog has undescended testicles.

However, the deeper we dive into the studies on the impact that neutering has on a dog's health, the more we seem to find conflicting studies. Studies have found that found that lymphoma(4), mast cell tumours(5) and hemangiosarcoma(6) are more common in spayed females than unspayed females, whilst another found that hip dysplasia and cranial cruciate ligament tears or ruptures were more likely in neutered than intact males and females(7).

If I am going to neuter my dog, when should I do it?

So, if you have decided that neutering your dog is the right thing to do, the next thing you need to consider is the best age to do it. Some vets recommend this procedure as early as 6 - 9 months, but this can be extremely detrimental as this doesn't give your puppy enough time to finish growing and mature fully. It can result in your dog being underdeveloped and can often lead to joint problems, particularly in larger breeds(8).

Whether your dog is male or female, the most important thing is that you give your dog time to finish growing before neutering. Even after they have stopped growing physically, they still need time to mature and for all the hormones associated with these changes to settle. Smaller dogs often mature faster than larger dogs, so the smaller your dog the sooner you can get it neutered. However we generally advise to clients not to consider neutering any dog until at least 2 years old because at this point you will have a much better idea of your dog's overall personality.

When it comes to males, alongside complete removal of the testicles, chemical castration is also an option if you are unsure on how it might affect your dog. Chemical castration generally involves an injection which lasts for about 6 months. During this time, it is helpful to note any changes you have seen in your dog, and also any changes that start to happen as it wears off. This can help you make an informed decision as to whether the castration would impact your dog in a positive or negative way.

With females, it is not advisable to spay them whilst they are in season (or having a phantom pregnancy). This is because the procedure is riskier as their blood does not clot as well when they are in heat and there is an increased blood supply to the reproductive organs so a higher risk of bleeding. Their hormones are also all over the place during this time and neutering them bang in the middle of this can mess things up even more. It is advisable to wait until after the dog's first season before spaying, and the reason for this is that we know that they are sexually mature at this point. However, we tend to advise letting your dog have two seasons, and this is because once you know how often they come into heat, you can spay them bang in the middle when their hormones are the most settled.


Whilst there are very few hard and fast rules when it comes to neutering your dog, two things are certain; it is important not to neuter your dog too soon, and it is certainly not a quick fix for behavioural problems. However, studies in the area are conflicting and can be extremely confusing, even for professionals. Every dog is different and there are so many variables to consider. The important thing is to not rush into neutering without having considered your dog as an individual. The important thing is to do your own research in order to make an informed decision that is best for your dog as an individual.

(1) Egenvall A, Hagman R, Bonnett BN, Hedhammar A, Olson P, Lagerstedt AS. Breed risk of pyometra in insured dogs in Sweden. J Vet Intern Med. 2001; 15(6):530–538

(2) Baioni E, Scanziani E, Vincenti M.C, Leschiera M, Bozzetta E, Pezzolato M, Desiato R, Bertolini S, Maurella C, Ru G. Estimating canine cancer incidence:Findings from a population-based tumour registry in northwestern Italy. BMC Vet. Res. 2017;13(1):1–9

(3) Blue Pearl Specialists. “Testicular Tumors in Dogs,” BluePearl Pet Hospital, 15 June 2017

(4) Villamil JR, Henry CJ, Hahn AW, Bryan JN, Tyler JW, Caldwell CW. Hormonal and sex impact on the epidemiology of canine lymphoma. J Cancer Epidemiol. (2009) 2009

(5) White CR, Hohenhaus A, Kelsey J, Procter-Gray E. Cutaneous MCTs: associations with spay/neuter status, breed, body size, and phylogenetic cluster. J Am Anim Hosp Assoc. (2011) 47

(6)Prymak C, McKee LJ, Goldschmidt MH, Glickman LT. Epidemiologic, clinical, pathologic, and prognostic characteristics of splenic hemangiosarcoma and splenic hematoma in dogs: 217 cases. J Am Vet Med Assoc. (1985) 193

(7) Witsberger TH, Villamil JA, Schultz LG, Hahn AW, Cook JL. Prevalence of, and risk factors for, hip dysplasia and cranial cruciate ligament deficiency in dogs. J Am Vet Med Assoc. (2008) 232

(8) Hart Benjamin L., Hart Lynette A., Thigpen Abigail P., Willits Neil H. Assisting Decision-Making on Age of Neutering for 35 Breeds of Dogs: Associated Joint Disorders, Cancers, and Urinary Incontinence. Frontiers in Veterinary Science 2020; 7


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