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.

03/1/16

Eat Less, Live Longer

Eat less, live longer

 

ResearchBlogging.orgLast year I went to a Primal Paws workshop in Adelaide, and Dr Jamie mentioned research which suggested that dogs that stayed skinnier lived longer healthier lives. Obviously, I had to know more, so I found the 2002 paper on Labradors.

Young Black LabradorThe basic design of this study (published in 2002) involved 48 labradors. Each labrador was buddied with another labrador at 6 weeks of age (choosing a buddy based on sex and body weight), and then one pup in the pair was fed 25% less than the other dog in the pair throughout life.

The focus on his study was basically to see the effect that 25% less food had on longevity and other illnesses in dogs. Apparently, many other studies have been done, primarily on rodents, that have shown that less food (regardless of many other variables) results in longer living and healthier animals. However, this research hasn’t been conducted on larger mammals. (This is the first study, that the authors know of, on dogs. Research on primates is ongoing.)

Each year, for at least 14 years, the dogs alive had bloods taken and body composition scoring. Also, their deaths and any diseases that occurred were recorded alongside the year of acquisition.

 

The main points:

  • Dogs that had less food’s median life span was significantly longer.
    Dogs who were fed less had a median lifespan of 13 years, compared to 11.2 years in their partners.

  • “The onset of clinical signs of chronic disease generally was delayed for food-restricted dogs.”
    For dogs who had oestoarthritis (which was 43/48 dogs), 43 of these dogs required treatment. For controlled fed dogs, first treatment was needed from 6.8 years to 12.9 years. In the restricted fed group, first treatments was needed from 7.9 years to 14.1 years. Mean age was 10.3 in controlled group and 13.3 in restricted group, which was statistically significant.
    39 dogs required treatment for 1 or more chronic conditions. “Mean age to which 50% of the dogs in each group survived without requiring treatment for a chronic conditions as significantly lower for the controlled-feeding group than for the restricted-feeding group.”

  • ”No signs of nutritional deficiency (eg, progressive weight loss and general or specific clinical signs of a nutrient deficit) occurred during the study.”
    It’s important to note that, even though 24 dogs were fed a lot less food, they were still healthy!

  • Dogs in both groups had increased body condition scores (i.e. were fatter) from 6-12 years.
    This is just an interesting tidbit that illustrates a lull in the body’s metabolism at this particular point of time.

 

Problems

It’s hard to know whether this study will be replicable in different breeds or different genetic stock. Considering the history in the duplicity of results in other species, I think we can be pretty confident these results are solid. However, more research does this would be great.

Even though 48 dogs is a pretty good number for a sample, a bigger sample size is always better.

One question I found myself asking throughout this is, if it’s better to feed less food of a higher quality to maintain weight, instead of more food of poor quality? This would also be a good area for further research.

Indi mourns over the understanding that it's better for her to have 25% fewer chips.

Roxy mourns over the understanding that it’s better for her to have 25% fewer chips.

 

Take home points:

  • Feed your dog less. It might live longer.
  • Feed your dog less. It might be longer before it needs treatment for oestoarthritis (if they develop the condition).
  • Feed your dog less. It might be longer before it needs treatment for any chronic condition.
  • Feed your dog less, especially once he turns 6 years old.
  • Point from the actual text: “We recommend that for purposes of health and longevity, dogs be fed to maintain a body condition score less than 5.”

I’ve never been happier with my decision to keep my dogs at a lean weight throughout life.

 

Reference:

Kealy RD, Lawler DF, Ballam JM, Mantz SL, Biery DN, Greeley EH, Lust G, Segre M, Smith GK, & Stowe HD (2002). Effects of diet restriction on life span and age-related changes in dogs. Journal of the American Veterinary Medical Association, 220 (9), 1315-20 PMID: 11991408

 

Further reading:

How to Reduce Your Dog’s Weight

02/24/16

CECS is a Gluten Sensitivity

ResearchBlogging.orgThe idea that CECS is a Gluten Sensitivity has been presented by recent research.

They were actually quite confident with the link between the two, saying in the research,

Canine epileptic cramping syndrome in [border terriers]s is a gluten-sensitive movement disorder triggered and perpetuated by gluten and thus responsive to a gluten-free diet.

This is pretty exciting stuff! CECS (short for Canine Epileptoid Cramping Syndrome, or sometimes called ‘Spike’s Disease’)  is an unusual condition found almost exclusively in border terriers. These dogs are normal dogs except for when they have an ‘episode’ or a seizure. During an episode, the dog will ‘cramp up’. Typically, they remain conscious, but can’t walk, and sometimes appear worried following an episode.

Chip, a border terrier that does not have CECS

Chip, a border terrier that does not have CECS

So far, there has been no real diagnostic test or explanation for the condition. In December 2013, a study looked at CECS, but it was an owner-survey, information-gaining exercise. Which is important, but doesn’t give us answers!

It was so important that it actually spurred this research. In the December 2013 study, 50% of dogs were found to ‘respond’ (i.e. have less episodes) on a gluten-free or hypoallergenic diet.

So now let’s welcome this lovely small study titled ‘The Clinical and Serological Effect of a Gluten Free Diet in Border Terriers with Canine Epileptoid Cramping Syndrome‘, which begins to look at how we can both diagnose and treat CECS. Exciting stuff!

The aim of the study was to work out if a gluten-free diet would effect dogs with CECS. Not only did the researchers want to know if the dogs stopped having episodes, but if their blood looked different with and without gluten. Naturally, they wanted to know if these things were correlated.

The dogs involved were 6 border terriers (an equal mix of male and female). Each dog:

  • Had had CECS for at least 6 months
  • Had been diagnosed with CECS via veterinary observation (including video)
  • Had had at least 2 CECS episodes
  • Had not tried gluten-free diets before

For interest sake, the average age of onset for CECS in this small sample was 2.6 years.

Winnie, another border terrier who does not have CECS

Winnie, another border terrier who does not have CECS

Once recruited, the dogs had blood taken and the owners were given instructions for the dog going on a total gluten-free diet (Hypoallergenic Canine Dry from Royal Canin). The dog underwent a general physical examine (and some dogs went through more intensive procedures, owners consenting) and all were determined to be healthy, beyond the presentation of CECS.

The blood was again taken at 3, 6, and 9 month periods.

The blood was tested for antibodies which are considered important in diagnosing gluten sensitivity in humans.

The blood of non-CECS border terriers was also taken and tested.

The owner was asked to keep a record of the incidents of CECS in their borders.

Are you ready for the results? They’re pretty compelling.

So all that changed in these border terriers’ lives was that they were put on a completely gluten free diet. With this one change, all of the borders terriers, when they adhered to the gluten free diet, stopped having seizures within 4 weeks. Three dogs did not have seizures at all once they started the diet.

Two dog owners, upon completion of the trial, accidentally fed their dogs treats with gluten… And the dogs had seizures again. So not only did a gluten free diet stop seizures, the reintroduction of gluten caused seizures.

Now let’s talk about “Dog 6″. Dog 6′s owner is the epitome of why these kind of studies, where dogs are left with their owners, are hard work! Throughout the study, Dog 6 was a dog that continued to have seizures. Dog 6′s owner presumably fed the dog the gluten free diet, but then allowed the dog to continue to graze on horse poo when out and about.  This issue wasn’t identified until late in the study and so Dog 6 was excluded from the serum results listed in this article. However, when Dog 6′s owner actually did was they were told and stopped the horse poo eating, Dog 6 stopped having seizures too! When Dog 6′s blood was tested 3 months after the study ended (but 3 months into the owner actually doing it right), that dog’s blood results was consistent with the other dogs, and it too had ceased having episodes.

Why is this study such a big deal?

Up until now, we have had no way to diagnose nor treat CECS. (In fact, one of the criteria established in the 2013 study of CECS indicated that if a dog fails to respond to epilepsy medication then it probably is CECS. Nice to know, but not a great deal of help.)

The blood results from these dogs showed high levels of relevant antibodies in affected dogs while they consumed a diet with gluten. The presence of gluten-associated antibodies could be used to diagnose CECS.

Clearly, a treatment has been identified too: avoid gluten!

Other areas that are of interest:

  • Signs of gastrointestinal upsets could be a sign of gluten problems, or of future CECS. Vomiting, soft stools, or belly grumbling was reported in 2 of the dogs featured in this study. The presentation of belly problems and CECS together can be an indication of just one problem – gluten sensitivity!
  • The story of ‘Dog 6′, to me, really shows the importance of owners in being vigilant. I feel that many dog owners take a rather lazy approach to food elimination diets, but elimination means to completely remove. If you don’t completely remove, you can’t say that it’s been tried!
  • In humans, celiac disease has sometimes been associated with a rash… Which makes me think back to the correlation between CECS and skin-conditions in borders identified in the 2013 study.

Another quote from the study:

These investigations support the hypothesis that CECS is a manifestation of gluten sensitivity, making this the first [sudden onset] movement disorder in veterinary medicine with a serological link to gluten.

What research from here?

This is a very small study, and it’s important that we do more research before making solid conclusions. This study itself suggests further research:

  • With a larger sample size
  • More research into the correlation of gastrointestinal upsets and CECS
  • A double-blind randomised placebo-controlled trial

But in the meantime, while we’re waiting to know more, these researchers (and I!) recommend that, if you have a border terrier with CECS, you switch the dog to a diet that eliminates all gluten foods.

 

Reference:

Lowrie M, Garden OA, Hadjivassiliou M, Harvey RJ, Sanders DS, Powell R, & Garosi L (2015). The Clinical and Serological Effect of a Gluten-Free Diet in Border Terriers with Epileptoid Cramping Syndrome. Journal of veterinary internal medicine / American College of Veterinary Internal Medicine, 29 (6), 1564-8 PMID: 26500168

 

Further reading:

Gluten Sensitivity Triggers Epileptoid Cramping Syndrome in Border Terriers

 

CECS is a Gluten Sensitivity

 

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