But Mammary Cancer!


A common justification for early neutering of bitches is that it protects against mammary neoplasia. However, many frequently cited references are over 40 years old, and this evidence has not been scrutinised with the benefit of recent developments in epidemiological methods and knowledge of potential confounders of the association between mammary masses and neutering, such as age, breed and treatment with synthetic derivatives of ovarian steroids.

One of the most frequently presented arguments for desexing is ‘mammary cancer’. It is commonly stated that desexing bitches reduces the risk of mammary cancer.

But as always, we must ask: What does the research say?

I love to answer questions like this, and so I have read quite a bit of research on mammary cancers in bitches. However, despite doing lots of reading, none of these research papers have made their way to my blog.

The reason? The research is very old and I am not compelled to review or examine such ancient research.

Why does old research matter? It’s easy to say that ‘biology doesn’t change’, and if it was so in the 1970s, then it must be so now. While that’s the case, our understanding on research methods and limitations is continuing to improve.

Regardless, even if we say that the research from the 1970s is as accurate as ever, compelling results are those that are replicated. While it’s nice to get one study that shows a link between mammary cancer and sex hormones, we need multiple studies with large sample sizes to prove this without doubt.

Using the studies considered in Beauvais et al’s 2012 systematic review, since the 1960s, there has been approximately fifteen (15) studies on mammary cancer in the bitch. That is, the last fifty-five (55) years, there has been one study on mammary cancer in dogs in ever four yearsThere are very few papers on mammary cancer, and those that do exist do not replicate past results.

So how old is the mammary cancer research? 

Beauvais et al.'s references in their systematic review on mammary tumours in bitches as affected by spaying.

Beauvais et al.’s references in their systematic review on mammary tumours in bitches as affected by spaying.

Again, if we use the studies considered in Beauvais et al’s 2012 systematic review, there were fifteen studies in all considered. Of those studies, only one (1) of those studies was completed in the last ten years. Further, eighty-six percent (86%) of the studies are more than fifteen (15) years old. So, basically: the research is old!

Nothing excites me like a review on literature. (You can imagine what I’m like at parties.) When I noticed a systematic review by Beauvais et al. on mammary cancer in dogs (published in 2012), I was excited as I hoped I would find some more recent studies. The study did not fulfil my hopes, and so I am left believing that more recent research simply doesn’t exist.

Interestingly, the researchers made comment that a systematic review (like they produced) had seemingly not been covered before. A systematic review is used to evaluate the strength of evidence and to consider bias. This type of research is common in medical literature, but not so much in veterinary.

The researchers considered the quality of the research for thirteen reports and found “Nine were judged to have a high risk of bias. The remaining four were classified as having a moderate risk of bias.” Indeed, some studies made claims (e.g. that neutering had a ‘protective effect’) but then failed to back up these claims with evidence.

Considering that only one study found an association between neutering and reduced risk of mammary tumours, and two studies found no evidence, there is not strong evidence that desexing reduces the risk of mammary tumours.

Check out the mammaries! My girl, Myrtle, is due to whelp in a week's time.

Check out the mammaries! My girl, Myrtle, is due to whelp in a week’s time.

What does the evidence say? 

Our results suggest that there is some evidence in one study that neutering is associated with a reduction in the risk of malignant mammary tumours (approximately 10-fold), amongst dogs from which samples and been submitted for histopathology, although there was no evidence that neutering after 2.5 years of age is associated with any change in the risk of malignant mammary tumours.

Basically, they concluded that there is weak evidence and there is “not a sound basis for firm recommendations“. There is some evidence that desexing before 2-5 years of age is beneficial, and also evidence that desexing before their first season may be beneficial.

The biggest faults in the existing research identified by Beauvais et al. included:

  • Research failed to control for age or breed.
  • No indication of age at neutering.
  • Little numerical data provided in publications (which limited this retrospective study).
  • Lack of consideration to bitches treated with ovarian steroids (and the effects this may have on research.)

When it comes to spaying bitches, it is important to recognise that the implications of a gonadecmomy on many aspects of the bitch. Not only does desexing affect the health and temperament of that bitch, there may be wider implications on the general population.

At the moment, vets vary in their opinion and recommendations, especially by country. I encourage owners to do their own research when making decisions for their pets.


Further Reading:Beauvais, W., Cardwell, J., & Brodbelt, D. (2012). The effect of neutering on the risk of mammary tumours in dogs – a systematic review Journal of Small Animal Practice, 53 (6), 314-322 DOI: 10.1111/j.1748-5827.2011.01220.x


Breeder Registration is Bollocks

It doesn’t take long for those involved in animal welfare circles to hear arguments for the implementation of breeder registration. Many advocates of breeder registration argue that such a scheme would cause some breeders to ‘reconsider’ breeding, and one less breeder is seemingly desirable to these animal advocates.

There seems to be a lot of faith and enthusiasm for such a scheme, despite breeder legislation never having been shown to achieve anything, that if affects ‘good’ and ‘bad’ breeders equally, impacts on rescues, and is difficult to police. Further, it seems to be targetting the mythical ‘overpopulation problem’, and not the actual issue of pound poor-performance.

So let’s address all the reasons why breeder registration is not the holy grail of animal welfare legislation.


No Evidence

There is no research that indicates that breeder registration reduces impounds/euthanasia, or improves the welfare of dogs in breeding establishments. For example, the Gold Coast Breeder Scheme is widely considered to be a flop, and has been discontinued. If there is no evidence that breeder legislation works, why would we be invest funds in establishing a scheme? Breeder legislation is a poorly qualified solution to animal impoundment, as much as BSL is a poor solution to dog bites.

It’s been tried before, and failed before, so why repeat the same mistakes?


Australian Shepherd puppies playing in a ball pit.

Decline in Ethical Breeders

The hallmark of most breeder registration schemes is a breeder having to pay in order to be ‘registered’.

The problem is that ethical breeders are (largely) not making money from their breeding, and therefore may not be in a financial position to pay for registration. Ethical breeders may choose to cease breeding due to expense. How do we ensure that responsible, ethical breeders are not discouraged from producing wonderful pets?

As most of these schemes require breeders to pay in order to be registered, what breeder registration effectively does is limit (legal) breeding to those who are making money from the practice. What I mean is: breeders who don’t make money are are probably the ‘ethical ones’, and are probably less likely to be able to afford registration. Are these the individuals we want to perturb from breeding?

Furthermore, there is those that breed dogs in working fields, like guide dogs, customs, and so forth. Any restriction on breeders would also cause more expense and process for those producing animals for these roles.


Unethical Breeders Unaffected

On the flip side of this, those who are most likely to be able to afford registration is puppy farmers themselves. Those running a business, profiting from the sale of puppies, are going to be able to afford registration, and continue breeding puppies.

If a breeder is raising puppies in conditions that are undesirable and outside of welfare codes, they are going to avoid registration, and simply remain unnoticed and unpoliced.

Or, alternatively, a breeder may pass all the codes as they meet physical levels of care, but they neglect the psychological well being of their dogs and puppies.

Basically: Unethical breeders are not going to be deterred by a breeder registration scheme.


Association with Code of Practice

Whenever breeder legislation is suggested, it tends to appear alongside a Code of Practice. A Code of Practice attempts to specify the way animals should be maintained. The biggest problem is that it effectively obligates breeders to keep their dogs in a kennel situation, which many would argue is in contradiction to the best interest of dogs. I discussed these problems in my article called Clean and Kennelled.

Basically, if you have a breeder registration scheme, it goes hand-in-hand with a prescribed approach to animal management and handling, which is counter intuitive to animal welfare goals.


Mandatory Desexing Overtones

Any breeder registration scheme has overtones of compulsory desexing for dogs. Not only are there legitimate reasons to keep dogs entire, mandatory desexing also has negative social factors. For example, mandatory desexing is often associated with increased surrenders (e.g. “I can’t afford to desex my dog, so I need to surrender it instead so I don’t become a law breaker”).

The Saving Pets blog does a good job of describing how mandatory desexing has never worked. Furthermore, I’ve blogged before about how mandatory desexing is hard to define (unless we desex everything and eradicate the species). Mandatory desexing is also often associated with early age desexing, which has its own welfare implications. And there’s evidence that making desexing mandatory increases surrenders, as people aren’t able to pay for the surgery and so are left with no other choice. And, on top of that, desexing is a medical procedure, which should be implemented by medical professionals based on the individual animal at hand – not policy makers.

Further, mandatory desexing seeks to categorise people who have an entire dog as ‘breeders’, when this may not be the case. That is, non-breeders may be forced to become breeders according to legislation in order to comply with the law.



Mandatory breeder registration often excludes key groups: ‘backyard breeders’, ‘working dog breeders’, and greyhound breeders. These breeders produce a lot of dogs and dogs that are, seemingly, more likely to end up in the pound system.

A dog is a dog. We can’t argue that breeder registration is for the welfare of dogs owned by a particular group of people. Legislation needs to apply to all dogs, or none at all.

And, when you make this breeder registration compulsory, you need to consider the impact on rescues.  As rescues occasionally take in pregnant dogs, they may be deemed as breeders, and may have to pay breeder registration too. The last thing we need is for rescues to be further out of pocket due to the introduction of unfounded legislation. I could list twenty things that rescue could be better suited to spend their funds on.


No Policing

I’ve blogged before about how many dog-related policies are not policed.  In South Australia, we have the Animal Welfare Act and the Dog and Cat Management Act. I see constant violations of both these acts as it currently stands. So what are we doing bringing in new legislation, when our existing legislation is under enforced?

Without enforcement, legislation is just tokensitic. Arguably, if our existing legislation was enforced, we wouldn’t need further legislation. Our existing legislation is pretty good legislation. If it’s not enforced, then puppy farms can flourish.


Poor Focus

My biggest rejection of this is that there isn’t a population problem. We don’t need to reduce the number of dogs in the world. Shelters need to market and promote animals in their care better. Breeder registration doesn’t have anything to do with shelter euthanasia rates.

While we’re busy spending all our time going after breeders, we will still be watching shelters killing a great number of dogs. While you might take issue with people breeding their dogs, I take bigger issue with shelters killing dogs in their community. What’s the greater problem here?


Further reading:

Just Stop Breeding Until the Pounds are Empty

Why I Don’t Want Oscar’s Law

The Fallacy of Mandatory Desexing

What is the answer? (To puppy farms)

Rescue Vs Breeders


The Week In Tweets – 9th October 2014

The ‘Week in Tweets’ is name in the optimism that I will post a Twitter round up on a weekly basis. This time it was a bit longer than a week… It’s basically my ‘recommended reading’ list. A lot of reading to do, so get ready!

This past week (ish, kinda) we were featured on the Top 50 Pet Blogs.

Over the next few months, I’ll be tagging some topics with ‘NDTF’. This is to cluster topics relevant to my recent Certificate III in Dog Training and Behaviour. I hope that if I tag future posts with NDTF, this will help future students in the subject.

Spike, one of Leema Rescue's current dogs available for adoption. More details on Spike here.

Spike, one of Leema Rescue’s current dogs available for adoption. More details on Spike here.


Tweet of the Week

A very personal post from Darren titled “How compassion fatigue infiltrated my life“.  While I haven’t got to the point of sharing my own story, needless to say, Darren’s story struck-a-chord with me. While it’s easy to see how the sheltering system does wrong by pets, it’s harder to see the very powerful impact the sheltering system has on humans. As always, the “Tweet of the Week” is the story you should read if you read nothing else.


Rescue and Sheltering

Shelter Solutions from Time4Dogs.

From Saving Pets: Izzy (and her little family), Australian rescue news, For those new to animal shelter reform, and Council shoots dog, dumps body, blames dog.

Sanctuary of Sorrow: Animals rescued from deplorable conditions.

US couple jailed for trying to save cat.

Excellent adoption promo video by the SPCA of Wake Country.


Dog Training and Behaviour

Impressive Feeding Routine.

Sterotypical dogs: repetitive and pointless?

Good Collar – Positive Reinforcement Dog Collar.

How to love your dog – it’s not what you think!

Crash Course Psychology Preview (so not specifically dog training, but).



The Ongoing Heartworm Controversy.

Dr Becker: The truth about spaying and neutering.

Hip Dysplasia; Common questions answered surrounding the illness.


Dog Breeds and Breeding

Puff the Magic Hund Dog from Time4Dogs.

Shakes and wails ’bout puppy dog tails.

Study shows purebred dogs not more sickly than mixed breeds.

K9 Online February 2014.


The Human-Animal Bond

Is caring for animals good for young people’s social development? from Companion Animal Psychology.

Boys in custody help care for pups.

Destruction of greyhounds distresses vet students.


Other Dog/Animal Stuff

Why the best dog seat belt may not be the best for your dog.

I’m so glad I had the camera! from Eileen and Dogs.

Brooks’ Books – Dogs to the rescue and giveaway.

The star coat pattern in foxes: what does it have to do with tameness?

Adelaide, remember when Samorn the elephant and George the orangutan lived at the zoo?



Odie had a good meet.

Rue and Myrtle. Friends.

Now called Bouncer. Available for adoption soon!

Rakow is looking for a home!

Feel sorry for the chicken that laid that.

Hannah before going in for desexing today.


Novelty (or Practical Habituation)

I have been thinking a lot of late about novelty in dog training. More technically, I’ve been thinking about habituation (i.e. a type of non-associative learning) and how it works in the ‘real world’ for changing dog behaviour in simple ways.


Dogs can habituate to water.

Dogs can habituate to water.

When I was a kid, I grew up with a chow chow called Ted. Ted mostly lived in the backyard, but as a child, I one day decided that Ted was going to get a walk every day. And so I walked him every day for about a month (before moving onto the next project, as kids do). Ted started the month with enthusiastic jumping regarding the prospect of a walk. He also vocalised a little bit. By the end of the month, Ted had the lead put on with no fuss, no jumping, no noise, and soldiered on for the walk.

Sure, I could’ve implemented some kind of training regime. But, in reality, I didn’t. Ted started the month thinking walks were novel, and his behaviour stemmed from this novelty. At the end of the month, he was habituated to the walk. Previously, the outside world meant a lot to him and resulted in him getting aroused. By the end of the month, it meant close to nothing, and his arousal levels were far less.


Then there’s our foster dog Bandit. I picked him up from his surrendering family, one hour from my house, and drove him home. He drooled, paced, and stressed the whole way home. On ever subsequent car trip, Bandit’s behaviour got more mild. Recently, I drove him to a boarding facility about 20 minutes away, and he was laying, asleep, by the time we got there. No training went into this. Bandit just ‘got over it’ because he habituated to the car – it became less novel.


I find many outside dogs are often ‘over the top’ when they meet people, and I think this is a novelty thing, too. If dogs only see people on an occasional basis (i.e. when you go outside), of course they’re going to be excited to see you! If they were inside and saw you constantly, their responses are going to be more mild. Indeed, with most attention seeking behaviours (e.g. jumping up, head nuzzling, vocalising), these behaviours will decrease if the dog has sufficient attention to start with. If attention is given liberally, the resource becomes less important, and the dog’s behaviour changes.


I think the concept of novelty is often overlooked in dog training. Sometimes, dog behaviour will ‘get better’ simply because the novelty of something wears off.

Doing many varied things often can do more than maintaining socialisation – it can reduce novelty and so also decrease undesirable behaviour associated with that novelty.


Labs and Goldens: Goldens get cancer better


A recent study, published in July this year, considered desexing in Labradors and Golden Retrievers and the long term health effects. This study doesn’t find anything revolutionary, but adds to the building body of evidence on the health impacts of desexing.

In the US, 83% of dogs are desexed, and often desexing is performed before 6 months of age. The popularity of this elective surgery has increased over the last 30 years. This is in contrast to many European countries, where animals are left intact.

This study considered 1015 Golden Retrievers and 1500 Labrador Retrievers. It used data on all Labs and Goldens admitted to a hospital between 2000 and 2012 (retrospective data). It mirrors a study on Goldens in 2013, and came up with similar results (which makes sense as it used a similar data set).

Dogs in the study were split by breed, then split by neuter status and age of neutering. So in each breed, there is a) desexed at <6 months, b) desexed at 6-11 months, c) desexed at 1 year, d) desexed at 2-8 years, and e) entire. (Dogs desexed at over 8 years were excluded from the study.)

While the study looked at lots of conditions, in particular it considered: hip dysplasia, cranial cruciate ligament tear, hemangiosarcoma, mast cell tumor, and mammary cancer. At times, the study lumped together ‘joint disorders’ and ‘cancers’, with the logic: Surely if we want to avoid any and all, not just one type of cancer or one type of joint disorder!


goldenphotoblogOn Joint Disorders

In both goldens and labs, the incidence of joint disorders in intact dogs (male and females) was about 5%.

Overall, though, it was found the earlier a dog was desexed, the greater the incidence of joint disorders.

In Labrador Retrievers, neutering at earlier than 6 months doubled (to 12.5% in males) the incidence of one or more joint disorder. Golden Retrievers faired even worse, with the same neuter-group having 4-5 times (27%) the incidence of one or more joint disorder.

Basically, there was a sliding scale: Golden Retriever males/females desexed at 6-11 months had a 14%/13% incidence of joint disorders. Golden Retriever males desexed at 2-8 years had a 10% incidence of joint disorders. While figures for Labrador Retrievers were not as high, they had a similar trend.

So, it seems from these results, the longer a dog is left entire, the healthier their joints.


On Cancers

While males in both breeds got off lightly when it came to neutering and cancer, and female Labradors were not much different, female Golden Retrievers drew the short straw.

There seems to be a ‘protective effect’ from gonadal hormones against cancers, especially in female golden retrievers.

The results reveal that neutering through 8 years of age [in female golden retrievers] increases the risk of acquiring at least one of the cancers at a level 3-4 times that of leaving the female dog intact.

Mast cell tumours didn’t occur in entire Golden Retriever bitches, but occurred at a rate of 6% in neutered bitches. Other cancers (lymphosarcoma, mast cell tumours, and hemangiosarcoma), in Golden Retrievers, also occurred more frequently in spayed than entire bitches.

Mammary cancers were only seen in Golden Retriever bitches (not in Labradors). 1.4% of intact female goldens were diagnosed with mammary cancer. If the bitch was neutered between 2-8 years, the incidence was increased to 2%.



Exclamation because I haven’t seen consideration given to pyo’ before in one of these studies. A good start!

In Golden Retrievers, the incidence of pyometra in intact females was 1.8%.

In Labrador Retrievers, the incidence of pyometra in intact females was <4%.



It’s interesting that, while the Golden Retriever and Labrador Retriever are similar in looks, function, and size, it’s interesting that they have such a marked difference in terms of their incidence of joint disorders and cancers.

For example, Goldens neutered at <6 months had a 20-27% incidence of joint disorders, while Labradors neutered at <6 months had a 11-12% incidence.

…for both breeds, neutering at the standard <6mo. period markedly and significantly increased the occurrence of joint disorders, although the increase was worse in the Golden than the Labrador.

Again, it’s important to recognise this is only part of a growing body of research looking at the long-term implications of desexing. We have had studies before that have suggested:

  • Desexed Golden Retrievers are two times more likely to experience joint disorders, and three times more likely to experience cancers, than their entire counterparts. (link)
  • In Vizslas, there is a higher incidence of cancer (mainly lymphosarcoma, hemangisoarcoma, and mast cell tumours) in desexed dogs than those intact. (link)
  • Osteosarcoma is two times more common in neutered dogs relative to intact dogs.
  • In Rottweilers, osteosarcoma was 3-4 times more likely to occur in rotties desexed before 1 year of age.
  • Cardiac and splenic hemangiosarcoma has a four and two times (respectively) greater incidence in spayed than intact females.
  • There is a higher incidence of lymphosarcoma in neutered females than intact.
  • Prostate cancer is four times more common in neutered males as intact males.
  • Cutaneous mast cell tumours are four times greater in incidence in spayed females than intact females.

One of the big arguments for desexing bitches is the fear of pyometra and mammary cancer in bitches. This study adds to growing evidence that mammary cancer isn’t as prolific as first thought. If you have an entire golden retriever bitch, your likelihood of experiencing mammary cancer or pyometra is 2.2%. If you have an entire labrador retriever bitch, your likelihood of experiencing mammary cancer or pyometra is less than 4%.

While many of the studies mentioned above are to do with cancers, there is evidence regarding the impacts of desexing on joints as well.

“The effects of neutering in the first year of a dog’s life, especially in larger breeds, undoubtedly reflects the vulnerability joints to delayed closure of long-bone growth plates from gonadal hormone removal”

Studies like this have implications for studies of cancers over all. It is useful for us to examine what dog breeds have which types of cancer, for future research purposes.

This study did not look at cognitive decline accelerated by neutering, but acknowledges that there is some evidence for this and it is a field for further study.


The Study:
Hart, B., Hart, L., Thigpen, A., & Willits, N. (2014). Long-Term Health Effects of Neutering Dogs: Comparison of Labrador Retrievers with Golden Retrievers PLoS ONE, 9 (7) DOI: 10.1371/journal.pone.0102241


Further reading: 
Potential Risks of Neutering and Age at Neutering for Golden Retrievers and Labrador Retrievers