07/16/17
Litter Size - Can we predict it?

Litter Size – What the research says

Litter Size - Can we predict it?

There is an ongoing paucity in the literature surrounding most dog matters, and that means dog knowledge is often based on anecdotes and experience instead of facts and figures. Dog breeding is no exception. Breeders will tell you that they get bigger litters if x, smaller litters if y, that they’ll never mate a bitch if z. While personal experiences can provide case studies, I am interested in much bigger data.

Enter a Norwegian study looking at 10,810 litters.

This study used data held by the Norwegian Kennel Club to look at every litter registered in 2006 and 2007, across 224 breeds. Statistical analysis was then done to determine all the wonderful figures summarised below.

The aim of this study was to determine what actually makes a difference in litter size. (Litter size being the number of puppies born, alive or dead.)

Firstly, an overall average had to be determined. For this data set, the average litter size, considering all breeds, was 5.4 puppies.

For those interested in average litter size by breed: The largest average litter size was in the Rhodesian Ridgeback with an average of 8.9 pups per litter. The Toy Poodle and Pomeranian had the smallest average litter size – 2.4 pups per litter. And the Border Terrier (because I’m biased) had an average litter size of 5.1 pups per litter.

This study found that litter size was influenced by the size of the breed, the method of mating, and the age of the bitch. Litter size was not affected by season of birth, or the number of litters a bitch had had.

Size of the breed

This study examined dogs based on average breed size. They were classed as miniature breeds (<5kgs), small breeds (5-10kgs), medium breeds (10-25kgs), large breeds (25-45kgs), and giant breeds (>45kgs). Bitches were recorded against the average size of a dog for their breed and not specifically on the size of that given bitch.

“When looking at all the … litters…, mean litter size increased with the size of the breed. The mean litter size was 3.5 in miniature breeds, 4.2 in small breeds, 5.7 in medium breeds, 6.9 in large breeds, and 7.1 in giant breeds.”

The feature of larger dog breeds having larger litters is not a new thing – this phenomena is consistent across other studies. But this study is different as it found that it wasn’t just size of the breed that mattered…

Age of the bitch

The first analysis of this data showed no significance with the age of the bitch, however, once breed size was taken into account, there were two trends apparent:

  • In small and miniature dogs, young and old bitches had smaller litters than the ages in between.
  • In larger breeds, increasing age corresponded with decreasing litter size. (Young bitches of larger breeds produced the largest litters – unlike small and miniature breeds.)

Predicted litter size by the age of the bitch for the five different breed size groups from Borge et al. study.These results are a little different to other studies, which have shown smaller litter sizes as bitches get older. (As in, the results this study got for larger breeds was seen in all breeds in previous studies.) It could be that smaller sample sizes in other studies may have missed this, or that other studies used larger breeds as their data set instead of small or miniature breeds. One suggestion is that small breeds may not mature as quickly as previously believed, and so they’re not able to reproduce until they reach that mark. (To me, this kind of makes sense – considering small breeds often live longer, then it’s likely that they mature more slowly, too.)

Method of mating

Like the age of the bitch, the first analysis on the data didn’t show a significance change in litter size based on mating method. However, when the data set was adjusted for breed, breed size, and age, naturally mated bitches had significantly larger litters than those who had been AIed (either fresh or frozen).

A decrease in mean litter size of 0.4 puppies would be expected for litters conceived with AI with fresh semen and 1.3 for AI with frozen semen, both compared to natural mating.

Things that didn’t matter

The number of litters a bitch had previously didn’t influence the size of her litter. (However, older bitches normally had had more litters – and their age did influence litter size.)

The season the litter was born in did not influence litter size.

Conclusion

Size of the breed, age of the bitch, and the method of mating are three factors work together in determining litter size. It’s not one thing – it’s all three.

“… the size of the breed, the age of the bitch and the method of mating were found to influence litter size in purebred dogs when controlling for breed, with the size of the breed as the strongest determinant.”

This study is better than past studies in this area for its huge sample size, its variety of breeds, and the fact that it considers all puppies in a litter (not just those registered, as some past studies have done). In this way this study is unique. It is probably a pretty reliable data pool for purebred dogs, too, as 90% of purebred dogs in Norway are registered with their kennel club.

Things to consider regarding the vigour of the results:

  • It’s a retrospective study.
  • It does not include data from litters where all pups were born dead.
  • Calculating mean litter size is hard, because of % made up of small or large breeds. Small breeds are currently popular, so could perhaps pull down the mean litter size seen in this study. Studies done in different countries, with different breeds being popular, is likely to result in different results.
  • There is a relatively small sample of bitches who were mated not-naturally in this study, so the results should be interpreted cautiously, however the results are consistent with previous findings.
  • This study only groups dogs by weight – not by body shape. This might yield differences. (A neapolitan mastiff is really different to a greyhound.) And they group them by weight average of breed, not the weight of the individual bitch
  • This study looked at only two years and the researchers wonder if there might have been more variation in season of birth if there was more time taken into consideration.

In conclusion: Based on this study, breed size is the strongest determinant for litter size in a dog. The age of the bitch and the method of mating were also significant predictors of litter size. These three things interact, making litter size predictions difficult!

Acknowledgements:

Borge, KS, Tonnessen, R, Nodtvedt, A, & Indrebo, A 2011, “Litter size at birth in purebred dogs – A retrospective study of 224 Breeds”, Theriogenology, 75, 911-919.

Thank-you to Waldwiese Kennels for the cover image – a litter of longhair weimaraner puppies.

09/6/14

The SA Story (Again)

selectcommitteesa

After hearing the ‘results’ of the Select Committee on Companion Animal Welfare in SA, I was hugely disappointed in the process and the recommendations. However, I was pleased to hear nothing further about it (it came out July last year!).

Until now.

A few articles (one | two | three) have come out quoting Ian Hunter (politician), Tammy Franks (politician), Tim Vasuedeva (RSPCA CEO), Steven Marshall (politician), and Jay Weatherill (politician).

The hot ideas are compulsory desexing (or just desexing puppies in pet shops), a code of practice, and a breeder licensing scheme, with some extra legislation thrown in for good measure. It’s not a surprise that this is mostly bad news, considering the spurious nature of the original Select Committee report.

 

Compulsory Desexing

The articles seem to be looking at both compulsory desexing, and compulsory desexing of all dogs sold in pet shops. The narrator in the first article describes the community as ‘divided’.

 

Compulsory Desexing of Petshop Puppies

Tammy Franks, in particular, supports the suggestion that all puppies from pet shops should be desexed.

Tim Vasudeva, from the RSPCA, says, “We’ve been desexing puppies between 3-4 months for years and years and we haven’t had any problems.”

The first article claims that the government will look at compulsory desexing of dogs sold in pet shop in light of a Select Committee’s report. While the report made many poor recommendations, desexing of dogs in pet shops before sale was not one of them! False reporting!

The problem with this is: We are desexing very young puppies and there is evidence that there are harms associated with desexing when it is done at a young age. These harms go beyond anaesthetic risks and immediate recovery (which is what Tim is referring to) and is more about long term acquisition of health problems including cancer. (You can read a recent study on golden retrievers, or a recent study on vizslas to learn more about this.)

Further, what is the point of this suggested legislation? Why should all puppies be desexed before sale? Especially because of the long term health risks?

If you wanted to get me on side with this suggestion, I would be more inclined to support the sterilisation of puppies before sale (including tubal ligation and vasectomies, that aren’t known to have these long-term health outcomes). However, I’d still be asking what the point of this was – surely there’s bigger issues for us to be dealing with.

 

Compulsory Desexing of Everything

Tim Vasudeva, from the RSPCA, says that the AVA’s research shows that desexed dogs are 2.6 times less likely to bite. This is not true: the AVA refers to others’ research, using 23 year old data, which suggests desexed dogs are 2.6 times less likely to bite.

Tim Vasudeva spoke about how desexing could be beneficial – in reducing wandering and hormone-driven behaviours and said “At the very least I don’t think can hurt”. While there is actually a study that indicates that this is the case, it is one old study. Anecdotally, I know of plenty of people who have non-humpy non-pissing non-wandering dogs that are entire.

Ian Hunter says that “In the ACT, desexing is compulsory and has led to a 47% decrease in dog attacks. It’s also reduced the number of unwanted dogs being euthanised.” Despite a lot of research on my part, I couldn’t find any evidence that this is the case. Any clues on this appreciated! While there might be a correlation (I stress might), this doesn’t indicate a causation.

 

Code of Practice

All three articles talk about the government introducing a Code of Practice to target puppy farms and makes sure dogs are kept and born into healthy and humane conditions.

But a Code of Practice will affect everyone, not just puppy farms! Such codes produced around Australia have pretty much banned dogs from being kept inside or on grass. Are puppy farms defined as those with lots of dogs? Those breeding many litters? Those producing many puppies? Anyone that breeds full stop? A ‘puppy farm’ is hard to define, and so Codes of Practice affect everyone instead.

Further, dogs already have to be kept in a humane way! The Animal Welfare Acts and similar legislation across Australia requires it. Anyone who is allowing their dogs to get matted, or not have water, or have medical treatments denied, is guilty of an offence. We can get puppy farmers for that! Code of Practice not required!

 

Licensing Scheme

I was excited in article two where there was the suggestion that there would be no licensing scheme… Then article three suggested there would be. I’ve repeatedly made arguments against breeder licensing (the most elaborate being here), but basically:

1) Breeder licensing hasn’t been shown to do much (like the Gold Coast scheme) – it doesn’t reduce pound intakes for sure. And puppy farmers don’t make a habit of signing up.

2) Why would we introduce a new license scheme, when the Animal Welfare Acts are not currently enforced?

3) How do we ensure that responsible and ethical home ‘hobby breeders’ are not discouraged from breeding wonderful pets?

4) Often, breeder licensing excludes ‘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.

 

Other Matters

Tammy Franks wants shelters to reveal euthanasia rates publicly. I think this is great if shelters were to have such transparency.

Article two and three suggest that mandatory microchipping will come in, and be compulsory (presumably, hopefully, compulsory before sale). While I have no qualms with microchipping being mandatory, I look forward to the phone line that allows me to report in those selling animals without microchips illegally. I don’t look forward to my expensive phone bills from making such reports. What I’m saying is: I have no confidence that this legislation will be adequately enforced.

Interestingly, one article says that there will be a “requirement for pets to only be bought from registered breeders”. That would be interesting! No more RSPCA, AWL, rescue group sales. No more guide dog and assistant dog groups selling unsuitable animals. Does that mean private rehomings are no longer legal? Surely this must be some kind of error in reporting.

And still there’s continued bleating about a cooling off period, under the guise that it would “reduce impulse buying and cut the number of pets being abandoned or surrendered”. There is no evidence that this is the case! Firstly, it does not seem that pets acquired impulsively are at any greater risk of being surrendered than pets acquired with a lot of thought. Secondly, there is no evidence that a cooling off period would reduce abandonment of pets. I don’t know how this even gets attention!

 

How unfortunate that the Select Committee’s recommendations are now gaining media attention and potentially some momentum in SA.

I spent a great many hours researching and writing my 20 page submission to the Committee. When the Committee published its findings and suggestions, I was so angry that the recommendations made were based on an emotive community rather than evidence and science.

I had been peacefully thinking that the Select Committee was just a little media stunt, and that it was going to disappear. These recent media reports and troubling and upsetting.

It’s concerning that the Government is prepared to invest resources into plans with no evidence that they will have any impact on animal welfare.

It is just as concerning that the community is lapping it up.

 

Further reading:

Public Misconceptions

Is desexing a cult?

Companion Animal Taskforce in NSW – Feedback

09/3/14

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.

 
Source:
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

07/1/14

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.

 

avadesexing

 

 

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.

06/23/14

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.

 

Reference:
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