A Link Between Desexing and Reactivity

ResearchBlogging.orgWhile desexing bitches is a common surgery, I was pleased to see Kim et al. take note that “the side effects of the operation, particularly any changes in behaviour, have been quantified in only few studies”.

That is to say, despite us commissioning vets to take the ovaries and uterus out of a great many bitches, we don’t really have much research about it. It’s a pretty scary state of play.

This particular study took 14 healthy German Shepherd bitches, between 5 and 10 months old. Half of these dogs were spayed, and the other half left entire. (The bitches were assigned to each group randomly, except for litter sisters, which were assigned opposite groups.)

After the spay, and having been given 4-5 months to recover from the surgery, the bitches were filmed in their kennel as a stranger and a dog approached. This footage was then scored based on how reactive the bitch was. A score of ’3′ indicated severe reactivity, and a score of ’0′ indicated no reactivity. The scorer was unaware of whether the bitch was spayed or not.

Photo courtesy of Rachel Willis.

Photo courtesy of Rachel Willis.

The reactivity of each bitch was recorded several times, and the reactivity of each bitch declined over the study. It’s likely that the bitches habituated to the novel stimuli. However, despite this affect, bitches in the ovary-hysterectomy group scored higher throughout the study.

Before generalising these results, there are some matters to consider:

  • Reactivity was only measured in a kennel setting, and how these dogs react in the ‘real world’ may be different. We can’t suppose that our pet dogs are going to respond in the same way as kennel dogs.
  • The reactivity of these dogs was not measured at the start of the study. While it is unlikely, perhaps more reactive dogs happened to fall into the treatment group by chance. Without a ‘before desexing’ score, we cannot be sure of this.
  • The authors make note that these results are for German Shepherd bitches aged 5-10 months old. We can’t assume dogs of all breeds and ages would respond this way to spays.
  • Further, the bitches in this study are working lined German Shepherds, which may be more reactive than the typical pet dog.


However, this study notes that other studies on bitch spays have shown that as a group spayed bitches are:

  • More likely to gain weight
  • More aggressive than prior to spay (if they were aggressive prior to spay)
  • More active
  • More likely to have urinary incontinence
  • More likely to be reactive after surgery


The authors recommend:

[V]eterinary practitioners should inform owners that a bitch may become more reactive after spaying either because they have lost the calming effects of progesterone or because elevated gonadotropins stimulate release of adrenal androgens.

Kim HH, Yeon SC, Houpt KA, Lee HC, Chang HH, & Lee HJ (2006). Effects of ovariohysterectomy on reactivity in German Shepherd dogs. Veterinary journal (London, England : 1997), 172 (1), 154-9 PMID: 16772140

Further reading:
Desexing: It’s bad for Vizslas too
Is desexing a cult?
Desexed dogs – 2.6 times less likely to bite!
Why would you NOT desex your dog??
Golden Retrievers: Cancer if you do, cancer if you don’t


Desexed dogs – 2.6 times less likely to bite!

Australian Veterinary Association makes this claim, in its PDF “Dangerous Dogs – a sensible solution“:

Entire (undesexed) dogs are 2.6 times more likely to bite than those that are spayed or neutered (desexed)

Are undesexed dogs really that risky?

I decided to read the three studies referenced individually.





Messam, LL, Kass, PH, Chomel, BB, Hart, LA 2008, ‘The human-canine environment: a risk factor for non-play bites?’, Veterinary Journal, 177(2); 205-15.

This study used data from 2003 (11 years ago) collected in Kingston, Jamaica and San Fransico, USA. Participants were recruited from vet clinic waiting rooms where they were presented with a questionnaire, set to determine the nature of their dog’s biting behaviour (and differentiating it from play biting).

When it came to comparing entire and gonadectomised dogs, this research suggests:

  • Intact dogs are more likely to bite than desexed dogs
  • Intact males are 1.68 times more likely to bite than desexed males
  • Intact males were 0.8 times more likely to bite than intact females
  • Spayed females were the ‘least bitey’


Guy, NC, Luescher, UA, Dohoo, Se, Spangler, E, Miller, JB, Dohoo, IR and Bate, LA 2001, ‘Demographic and aggressive characteristics of dogs in general veterinary caseload’, Applied Animal Behaviour Science, vol 74, iss 1. 

This research is based on data collected in Cannada in 1996 (18 years ago), targeting owners with a questionnaire waiting for vet appointments in three Canadian provinces. Their results indicate:

  • The lowest level of aggression (biting and growling) was reported in intact female dogs
  • Intact male dogs were twice as likely to have bitten as intact female dogs
  • Intact male dogs and neutered females incidents of biting was reported at a similar level

And to quote:

“Relative to intact female dogs, neutered male dogs of at least 1 year of age were at the highest risk for having previously shown biting behaviour, followed by neutered female dogs, and intact males… [O]ur results indicate that the behavioural outcomes of [neutering] are worthy of further investigation.”


Gershman, KA, Sacks, JJ & Wright, JC 1994, ‘Which dogs bite? A case-control study of risk factors’, Pediatrics, 93 (6 pt 1), 913-7. 

This study used data from 1991 (23 years ago) using 178 dog bites requiring medical treatment of a non-household-member in Denver, USA. Data was only used for dogs that had not bitten before. The study itself recognises this is a small sample size.

Their data concludes:

  • not-neutered dogs were 2.6 times more likely to bite
  • chained dogs were 2.8 times more likely to bite
  • dogs living with a baby were 3.5 times more likely to bite
  • male dogs were 6.2 times more likely to bite


So, are entire dogs 2.6 times more likely to bite?

If you are looking at the study in Denver, USA, in 1991 (23 years ago!) then, yes, their conclusions indicate that intact dogs are 2.6 times more likely to bite than desexed dogs.

But the other evidence referenced by the AVA does not make the exact same conclusions. The study conducted in 2003, using data from Jamaica and the USA, found that intact males were 1.68 times more likely to bite than castrated males, and 0.8 times as likely to bite as intact females. (This study is also old, with the data being collected 11 years ago.)

And that other article, with data from Canada in 1996 (18 years ago) makes pretty much the opposite conclusion. They found that neutered male dogs were the riskiest in terms of bites.


Questions to ask…

Why are we relying on data over a decade (or two decades) old? If aggression in entire dogs was a common phenomenon, surely we would have countless studies showing this problem.

Where is the Australian data-set?

Where is the study that controls for factors such as selectionsocialisation, and socio-economic factors?


What the AVA should really be saying is:

According to one study conducted in Denver, USA, 23 years ago, entire dogs were found to be 2.6 times more likely to deliver a bite (that required medical treatment) to a stranger than desexed dogs.


Scottie Cramp

ResearchBlogging.orgWhile reading up on CECS in border terriers, I happened upon a condition called ‘Scottie Cramp’. I was keen to learn more, and found the article “Hyperkinetic episodes in Scottish Terrier dogs” (and, more importantly, the reproduction of its text on the Scottish Terrier Club of America website).

Scottish terriers. Photo courtesy of Argowan Scottish Terriers. (Photo for illustration purposes - these dogs do NOT have scottie cramp.)

Scottish terriers. Photo courtesy of Argowan Scottish Terriers. (Photo for illustration purposes – these dogs do NOT have scottie cramp.)


What is ‘Scottie Cramp?’

‘Scottie Cramp’ is the popular term for hyperkinetic episodes in scottish terriers. This is a central nervous system problem that causes the hindlegs of effected Scottish Terriers to ‘cramp up’ so they kind of ‘skip’ with their hindquarters.

This condition is often brought on by excitement or exercise, and gets worse as exercise progresses. Generally a walk of 90m-600m was enough to bring about symptoms in affected dogs in this study. (However, there was one badly effected dogs who displayed symptoms after 10m.)

Usually a dog will exhibit symptoms before 18 months of age, and this condition does not seem to affect the dog’s lifespan.


What does it look like?

The paper does a pretty good job of describing this disorder. So here’s what they say with some added emphasis from me:

During exercise, the onset of a hyperkinetic episode was usually indicated by a slight abduction of the front legs, resulting in an arclike motion of the limbs while extending.  The back then became arched in the lumbar region, and the hind legs were quickly over­flexed and then swiftly returned to the ground.  This motion has been appropriately described as a “stringhalt” gait.

The front legs became increasingly stiff, and while walking were quickly ex­tended then flexed. In rare cases where the back was not arched, the dog walked with a “goose step” gait. Forward movement was usually hindered, and in severe cases was completely absent, resulting in the dog walking in place. Facial muscles did not ap­pear to be affected at this time…

Occasionally, when the younger dogs were running, the hindquarters would suddenly and strongly become elevated, often to such a degree that the dog somersaulted. If the inducing stimulus was continued, the hind legs became increasingly resistant to flexion, which finally resulted in a pillarlike stance, with the dog unable to walk. If the dog fell down, it would curl into a ball with its head, limbs, and tail tucked in; breathing would ap­pear to cease. The severe seizure would last approximately 15 seconds, after which the dog appeared relaxed and panting. During or just preceding a severe episode, the facial muscles were often affected, and the dog was unable to open its jaws.

None of the dogs lost consciousness during an episode, nor did they appear to be in pain. A short period of rest would alleviate the hyper­kinetic episode in most dogs, but the signs would quickly reappear if the inducing factors were not eliminated.

Here’s a video showing a scottie with this cramping disorder, and a ‘normal’ scottie:


What causes it?

This was a small study of only 10 dogs, but the results seem to indicate: “Excitement and fear facilitated the hyperkinetic episodes, whereas anxiety and apprehension were often inhibitory”. (Personally, I am not sure that fear and anxiety are different enough to form this kind of conclusion.)

They also found that amphetamine sulfate, when injected intramuscularly, caused symptoms within 15 minutes.

There was a lot of variation between dogs and symptoms, but it seemed that frequent exposure to the trigger, the dogs tended to build tolerance. However, no dog ‘recovered’ (i.e. ceased to display symptoms).


What fixes it?

As this is a Central Nervous System problem, drugs that target the CNS, naturally, are effective.

Symptoms can be alleviated by some drugs (such as chlorpromazine, acepromazine, and diazepam) injected intramuscularly. In the case of chlorpromazine, injection intramuscularly during a seizure caused cessation of symptoms within 15 minutes.

Diazepam worked to stop dogs seizing, and also to prevent seizures (given twice daily to affected dogs).

While Vitamin E has been anecdotally suggested as a preventative, this study did not find it to be effective.


How is Scottie Cramp diagnosed?

3 criteria for scottie cramp:

1) abnormal gait or seizures during excitement,

2) injected amphetamine should induce an episode, and

3) administering diazepam or promazine during a seizure should cause prompt remission.


Meyers KM, Lund JE, Padgett G, & Dickson WM (1969). Hyperkinetic episodes in Scottish Terrier dogs. Journal of the American Veterinary Medical Association, 155 (2), 129-33 PMID: 5816228


Vaccinations Last At Least Three Years

ResearchBlogging.orgWhen reading Terrierman he made reference to the work Schultz has done on the duration of vaccines. Intrigued, I decided to read one of his articles. I dug up a review Shultz wrote on the duration of vaccines. It looks at available research on vaccines and their ‘duration of vaccinal immunity’ (i.e. how long they last).

Whether a dog has immunity can be determined either by antibody titres (a ‘titre test’) or a challenge study (e.g. deliberately exposing the dogs to the pathogen).


For distemper, parvovirus, and adenovirus the published data suggests an immunity period of 3 years or longer minimum.

Using blood products to test immunity, it seems that vaccines last 3 years or longer.  When using challenge studies, dogs that were vaccinated 11 years ago did not contract the virus.

According to this article, if a cat or dog is:

  • Vaccinated with core vaccines at 12 weeks of age or older,
  • Is revaccinated at 1 year old, and
  • Receives a vaccination “not more often than every 3 years”

then this would be as protective to the pet as annual vaccination.

However, non-core vaccinations last a year or less.

Table 1 shows estimated minimum duration of immunity for the 4 core canine vaccines.

How long does a dog vaccination last?

Shultz concludes, “Extending the revaccination intervals for canine and feline core vaccines does not place the animal at increased risk to developing vaccine preventable disease, but it does reduce the potential for adverse reactions”

He also recommends using titre tests to ensure that a puppy’s final vaccine enduces an immune response – and to revaccinate if the titre does not indicate that an immune response was produced.

Oh, and on cats? According to this paper, feline vaccines less researched, but feline parvovirus, calcivirus and herpes seems to last at least 7.5 years. Exception is feline leukemia which provides immunity for 1 year or less.


Ronald D. Schultz (2006). Duration of immunity for canine and feline vaccines: A review Veterinary Microbiology, 117 (1), 75-79 DOI: 10.1016/j.vetmic.2006.04.013


Aggressive Breeds via Owner Accounts

Establishing ‘aggressive breeds’ without using dog bite data: Using owner reports to establish the most aggressive dog breeds


ResearchBlogging.orgIn 2008, data was published on the ‘most aggressive dogs breeds’, with dachshunds, chihuahuas, and jack russells, coming out on top. Recently, various media reports having been reappearing on my newsfeed on this study, with titles like “The 3 Most Aggressive Breeds Revealed“.

Before we begin, please do acknowledge that I adamantly against BSL. I am heavily influenced by research and evidence and, currently, all the evidence points to breed specific legislation never being effective in reducing the incidence of dog bites, in any place globally.

That being said, because I am interested in science, I am interested in studies like this.

So what can this study teach us about aggression in particular dog breeds?

Cindy the Jack Russell Terrier: In the top three aggressive breeds according to this study.

A Jack Russell Terrier: in the top three aggressive breeds according to this study.


The Flaws in Breed Aggression Research

Aggression is a difficult characteristic to assess in dogs.  There are a variety of methods that researchers have used, and all have their ‘downsides’.

Using dog bite statistics is not the best course, as most dog bites go unreported, the dog breeds involved cannot be verified and, even if they are verified, it is impossible to understand how many dogs of that paricular breed exist in the community.

If you’re only looking at caseloads from behavioural clinics, then this data is likely to be biased.  Generally, people with larger and more dangerous (because of their size) dogs are more likely to seek help, as are people who have dogs aggressive to members of their family. (This article doesn’t mention it, but finances also play a role here – only those owners with the finances to attend behavioural clinics would be represented in such a study.)

There has been some popularity in behavioural tests (cough – D&CMB proposal – cough) where they do threatening or scary things to a dog and score their responses.  The problem with this is how this actually relates to the ‘real world’ and the aggression the dog displays in everyday life.

When you ask owners about their dog’s behaviour, their experiences and responses are subjective. And ‘experts’ aren’t much better, with many of them representing ‘shared stereotypes’ whether conclusions from their own experiences.


Study Design

In this particular study, C-BARQ was used. C-BARQ has a good record as being pretty reliable when it comes to asking owners what their dogs are like, temperamentally.

Members of 11 AKC club (‘club sample’) and vet clinic clients (‘online sample’) were invited to partake.

1,553 C-BARQs were completed by the club sample, with 29 excluded as they did not meet criteria.

8,260 C-BARQs were completed by the online sample, with 1,257 excluded for being mixed breeds or with no breed indicated, and 2,051 excluded as there was less than 45 of that breed represented – so in the end the sample was 4,952 responses for 33 different breeds.

They were rated on aggression towards strangers, owners, and other dogs.


Summarised Findings

The online sample and breed club sample differed in some ways.  Breed clubs submitted more intact dogs, more female dogs, and older dogs than those in the online sample. Despite this, the results were quite consistent across the two samples.

Dog aggression was the most common and most severe type of aggression in the study, but dog aggression was not correlated with aggression to people. This supports the widely held view that ‘dog aggression’ does not indicate a risk to people. Similarly, aggression towards household-dogs was not associated with aggression towards other dogs or people. From the data in this study, more than 20% of Akitas, Jack Russell Terriers, and Pit Bulls had serious aggression towards unfamiliar dogs.

When it came to aggression towards people, the highest rates were found in smaller breeds, ‘presumably’ because aggression from smaller (and so more manageable and less dangerous) dogs is more tolerable.

When it came to aggression towards owners, more than half of the aggressive displays towards owners were associated with the owner taking food or something else away from the dog.

While fear in animals is associated with aggression, fear was not strongly correlated with aggression in this study. Some dogs were aggressive but not fearful, some were fearful but not aggressive, and some were fearful and aggressive.

A quote from the study on their findings,

“Although some breeds appeared to be aggressive in most contexts (e.g., Dachshunds, Chihuahuas and Jack Russell Terriers), others were more specific. Aggression in Akitas, Siberian Huskies, and Pit Bull Terriers, for instance, were primarily directed toward unfamiliar dogs. These findings suggest that aggression in dogs may be relatively target specific, and that independent mechanisms may mediate the expression of different forms of aggression.”

Screen shot 2014-02-02 at 5.01.31 PM

Further results on a more breed-by-breed basis (breeds listed alphabetically):

  • Akitas rated higher for aggression towards other dogs than other breeds.
  • American Cocker Spaniels rated higher for aggression towards their owners than other breeds.
  • Australian Cattle Dogs rated higher for aggression towards other dogs than other breeds, and also rater higher for aggression towards strangers.
  • Basset Hounds rated higher for aggression towards their owners than other breeds, but were below average when it came to stranger directed aggression.
  • Beagles rated higher for aggression towards their owners than other breeds.
  • Bernese Mountain Dogs were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression.
  • Boxers rated higher for aggression towards other dogs than other breeds.
  • Brittanys were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression.
  • Chihuahuas rated higher for aggression towards people (both owners and strangers) and higher for aggression towards other dogs than other breeds.
  • Dachshunds rated higher for aggression towards people (both owners and strangers) and higher for aggression towards other dogs than other breeds.
  • English Springer Spaniels rated higher for aggression towards other dogs than other breeds, and also rated higher for aggression towards owners. Showed bred English Springer Spaniels were more aggressive than field bred lines.
  • German Shepherd Dogs rated higher for aggression towards other dogs than other breeds.
  • Golden Retrievers were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression.
  • Greyhounds were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression.
  • Jack Russell Terriers rated higher for aggression towards people (both owners and strangers) than other breeds and higher for aggression towards other dogs than other breeds.
  • Labrador Retrievers were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression. Field bred labradors were more aggressive than show bred labradors.
  • Pit Bulls rated higher for aggression towards other dogs than other breeds.
  • Siberian Huskies ranked below average on stranger directed aggression.
  • West Highland White Terriers rated higher for aggression towards other dogs than other breeds.
  • Whippets were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression.


Warning against reaching conclusions on the genetic basis of aggression…

The authors caution, “Demographic and environmental risk factors for the development of canine aggression need to be investigated across a variety of breeds so that both generalized and breed-specific influences can be identified.”


So what do you think? Are these studies results consistent with your experiences?



Deborah L. Duffy, Yuying Hsu, & James A. Serpell (2008). Breed differences in canine aggression Applied Animal Behaviour Science, 114 (3), 441-460 DOI: 10.1016/j.applanim.2008.04.006

View PDF.


Further Reading

More on C-BARQ: Can breeders breed better?