Should male dogs be desexed?

should male dogs be desexed?
After reading that desexing may not be necessary, Dr Andrew Spanner started researching the literature and comparing it to his own clinical experience. Photography:Simon Casson

Should male dogs be desexed? The answer may not be as simple as you think. By Kerryn Ramsey

The current debate surrounding the desexing of male dogs is a complex one, much discussed across the veterinary community. It’s not as simple as saying desexing is good or bad—it’s about the value of evidence and good science leading to good advice. While the average layperson thinks that getting their male dog neutered will create a placid, easygoing animal, this is simply not the case. 

Traditionally, male dogs were desexed to help control their aggression, stop them reproducing and limit indoor urination. These goals were successfully achieved but recent studies have revealed that the after-effects of desexing can be far more complex.

Behavioural problems

Paul McGreevy, Professor of Animal Behaviour & Animal Welfare Science at the University of Sydney, co-authored a study that investigated behavioural problems in entire and desexed male dogs. His results revealed that desexing may not be the best way to deal with problem behaviours.

“It came as a surprise to almost all of us but subsequent papers have confirmed what we found,” says Professor McGreevy. “Of the behaviours we saw frequently in desexed dogs, eight related to fearfulness and seven related to aggression. Of course, a lot of aggression in dogs derives directly from fear, so we need to consider the prospect that life without testosterone may make dogs more fearful.”

Age and weight

What became apparent in the study was the importance of the age at which dogs are desexed. Current AVA guidelines state that desexing can be performed as early as eight weeks and at a minimum of one kilogram of body weight. Professor McGreevy’s study found that the later in life a dog was desexed, the more he indoor urine-marked and howled when left alone, compared to dogs that were desexed earlier in life. However, dogs desexed later in life were reported to show less reporting of 24 other problem behaviours. 

“Our study shows that a number of behaviours are impacted by the timing of desexing,” says Professor McGreevy. “We need to discuss the importance of allowing the dog to mature skeletally and behaviourally prior to desexing.”

Dog welfare

The upshot of this is that the two most common reasons for desexing—indoor urination and howling—were reduced in desexed dogs. It’s also an effective and simple way to help control the dog population. But whether there’s a benefit for dog welfare is a more complex question.

“We are destroying far too many dogs due to their behaviour problems,” says Professor McGreevy. “Behaviour is the biggest killer of young dogs. Our study shows that desexing dogs can lead to unwelcome behaviours relating to fearfulness and aggression in desexed dogs. These behaviours often lead to dogs being surrendered to pounds. So, while desexing can reduce the number of unwanted dogs, it can also increase the chance of behaviours that will send dogs to pounds and to be ultimately euthanased.”

Data comparison

Dr Andrew Spanner of Walkerville Vet in South Australia is also interested in the desexing debate. He was aware that Professor McGreevy’s study stated that desexing male dogs can cause behaviour problems. It seemed so counterintuitive that he decided to undertake his own research. 

“Our study shows that a number of behaviours are impacted by the timing of desexing.”

Paul McGreevy, Professor of Animal Behaviour & Animal Welfare Science, University of Sydney

“I looked at all the studies that compare the behaviour of male dogs before and after desexing, and there are very conflicting results,” says Dr Spanner. “Some papers say that aggression is more likely in desexed dogs. Some papers say that aggression is less likely in desexed dogs. However, if you look at the more severe forms of aggression, there seems to be a very clear trend towards desexed dogs being less likely to cause significant problems such as bite injuries.”

Types of aggression

When comparing desexed and entire male dogs, it all depends on the type of behaviour and aggression being considered. Dr Spanner believes the most important thing to consider is human-directed aggression. This type of aggression is often against children, can cause a severe injury, and the dog is usually euthanased.

“Most of the aggression we see in private practice is fear aggression,” says Dr Spanner. “Fear aggression is much more to do with the choice of puppy and how it is raised than any other factor. Desexing will have very little effect on whether a dog is fear aggressive or not. A problem with a lot of the studies I read was that the different forms of aggression were not separated.

should male dogs be desexed?
Professor Paul McGreevy has studied the effecs of desexing on behaviour. Photography: Adam Taylor

“Any vet who’s working in practice will have seen that desexing generally reduces aggression. Dogs that are not desexed as they transition from puppy to adult are more likely to exhibit human-directed and dog-directed aggression. It’s one thing to talk about the literature, but it’s another thing to talk about veterinary experience. We should be careful to use evidence wherever possible, but most vets who have worked for more than five years in practice would know that desexing reduces aggression. I think we should respect that.”

Effective socialisation

Professor McGreevy believes that to significantly reduce aggressive behaviours, more emphasis must be placed on good socialisation in young dogs. This can proof dogs against fearfulness in later life.

“We really need to take advantage of the socialisation period that ends at around 14 weeks,” says Professor McGreevy. “It’s very important that we capitalise on that opportunity and expose the dog to everything that will become normal in its world. After 14 weeks of age, dogs encountering unfamiliar stimuli often regard them as a potential threat. During the socialisation period, the dog needs to be around other dogs and humans, and not just the human household but all kinds of people it may later encounter—men, women children, men with beards, people of different ethnic backgrounds, people pushing prams or shopping trolleys.”

Crunch time

The decision to desex male dogs is much more complex than previously thought. It’s no longer a simple binary issue. Each owner, each dog, each breed and each situation has to be considered. 

“Some of the factors that are going to be important in making that decision are the breed of the dog, the ability of the owners to manage an entire male dog, and their willingness to undergo dog training,” says Dr Spanner. “Additionally, some owners find it very hard to stop their dogs becoming obese once their dogs are desexed. The one big health risk of being desexed is the increased chance of obesity in most dogs. So dogs that live with owners who have trouble managing food intake may be better not desexing if their temperament is otherwise good.”

“I looked at all the studies that compare the behaviour of male dogs before and after desexing, and there are very conflicting results.”

Dr Andrew Spanner, Walkerville Vet

For the past three years, Dr Spanner has been advising his clients not to get medium and large breed dogs desexed until they reach their adult size. This usually happens between 12 and 18 months.

“We ask them to delay desexing because of three studies that were done on German shepherds, labradors and golden retrievers,” says Dr Spanner. “Each study looked at the prevalence of joint disorders in these three breeds based on whether they were desexed before six months, after a year or not at all. The results showed that the rate of cruciate ligament disease and hip dysplasia were lower in the dogs that had been desexed after a year of age and in dogs that were never desexed. The disease rates were much higher in dogs that were desexed before six months of age.”

Hot debate online

To further increase the knowledge base relating to companion animal disorders, Professor McGreevy developed a database called VetCompass Australia. It draws data from veterinary practitioners across Australia and is expected to reveal the prevalence of unwelcome behaviours in Australian veterinary practices. 

“We’ll soon be able to compare the Australian experience with the British report,” says Professor McGreevy. “The British data showed that the biggest threat to the lives of young dogs was their behaviour.”

Dr Spanner believes it’s important that vets today are flexible in their approach to desexing. Clients are much more empowered by the presence of the internet and they’re receiving lots of different information. Often dog owners are paralysed by an excess of information and by strong opinions on each side of the argument. 

“Despite what appears to be a very hot debate online, most dog owners trust the opinion of their veterinarian,” says Dr Spanner. “Most dog owners make the decision on whether to desex based on the advice of their veterinarian. We’re in a fortunate and responsible position with almost no vested interest in the debate. As long as there’s no harm to the dog, we can’t have a one-size-fits-all policy anymore. It’s important that we get it right.”

Of course, there are great reasons for desexing dogs. Professor McGreevy’s study is not suggesting they are of negligible importance but sometimes they are offset by far more unwelcome behaviours that relate to fearfulness and aggression in desexed dogs.

“It’s clear to me that we need to do more to socialise and train dogs comprehensively,” says Dr McGreevy. “That may mean more than attending just one a puppy class per week during the socialisation period. I’ve been studying dog behaviour for 25 years but there’s still an enormous amount to discover about how dogs behave in the human domain.”

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