Tuesday, 18 January 2011

Hybrid vigour... fact or fiction?

Illustration: Kevin Brockbank
So which is healthier -  posh pedigree or humble mutt? It’s this question more than any other that makes breeders of the purebred dog hyperventilate. And you can understand why. Surely, after years of honing their beloved breeds, their dogs are vastly superior in terms of health than their crossbreed cousins – especially, God forbid, than those awful designer dogs.
The breeders on the show-focused Champdogs website certainly think they know the answer. They recently had a big whinge about the prices of Labradoodles, Cockapoos and other money-earning crosses and, over 100 posts later, they emerged having convinced themselves that their purebred dogs had to be healthier. Phew!
“There’s no such thing as hybrid vigour in dogs,” was one comment, oft-repeated. “You only get hybrid vigour if you mate two species together and all dog breeds are the same species.”
Well no. While it is true that a lion/tiger cross would produce a hybrid animal, the term hybrid vigour is used more usually in science and agriculture to describe the rude health/better yield you get by breeding animals or plants of different varieties. Indeed, we enjoy the benefits of it every day in our food. Your morning toast? Very likely to be bread made with hybrid wheat. Your steak for supper? It may say Aberdeen Angus on the packet, but it only has to be 60 per cent purebred to be allowed to use the moniker. Same goes for eggs, chickens, corn-on-the cob and many other foodstuffs. The reason farmers use crosses is because the wheat grows stronger, the maize grows sweeter, the poultry thrives better and the cattle grow bigger. Indeed, the hybrid vigour so dismissed by dog breeders is one of the things keeping our farming industry afloat (if barely). That’s not to say that farmers don’t maintain purebred lines too – they do. But it’s often a more expensive business because the yield is less.
In fairness, one informed poster acknowledged this. She wrote: “You can get hybrid vigour when crossing two separate 'types' which have been kept pure in their own gene pools for some time. The theory is that over time, 'inbreeding depression' sets in with any closely-bred/line-bred strain, which is immediately lost when crossed to a different strain.” This is exactly right. But she then added:  “Of course if you cross two breeds that get epilepsy, or two breeds prone to hip dysplasia, or PRA (progressive retinal atrophy) - all you're going to get is epilepsy, HD or PRA. No amount of hybrid vigour can wipe away recessives present on both sides.”
This post goes hand-in-hand with another one that’s repeated with depressing regularity by breeders on many websites – and that is: “If you mate two different breeds the puppies will be cursed with all the problems of both breeds.”
Again, it’s not the case – although there is some truth in this.  Many conditions in dogs are recessive. That means that both parents must carry and pass down the genetic mutation that causes that condition for the pups to be affected. If they’re different breeds, this is much less likely, as confirmed by the Animal Health Trust: “Because of the small gene pool in purebred dogs, inherited diseases resulting from single gene mutations are more likely to occur than in their cross bred cousins,” said the AHT in a recent press release.
Of course if both breeds suffer from the same condition, the pups could be affected. There’s very good evidence, for instance, that Labradoodles  are just as likely to suffer hip dysplasia as their purebred parent breeds.  The breed mean hip score for Labradors is 15 and for Standard Poodles it is 14 while the Labradoodle’s average hip score is 14.  Over 400 have now been tested  via the KC/BVA scheme– more than many Kennel Club breeds, including the Boxer and Dalmatians – and clearly the cross doesn’t bring any benefits in terms of joint disease. This is as you might expect, but it isn’t a given. Both Springer Spaniels and Irish Setters suffer from the eye condition PRA, for instance, but it’s caused by different mutations. The Springer x Setter pups, therefore, will not go blind.
There’s another point here, too: dogs from genetically-different parents are likely to have stronger immune systems. This may not help with avoiding genetic disease, but it most certainly helps in terms of withstanding infections, parasites, viruses, auto-immune diseases and allergies. So here again, crossbreeds tend to have the advantage.
Next up on Champdogs was this old chestnut: “All my pedigree dogs are perfectly healthy but my mongrel has lots of problems, including epilepsy.”  No doubt this is the case – but I could chip in with evidence that all my mutts enjoy rude health whereas my purebreds are more sickly. It doesn’t prove a thing. To know which is more representative you have to compare a lot of crossbreeds with a lot of purebred dogs. Has that ever been done? Champdogs didn’t think so: “The claims about crossbreeds being healthier than pedigrees are based on unproved statistics” wrote one poster and no one chipped in to point out that they were wrong.
And they are wrong. There are several scientific studies which have explored the issue and found either no difference or that crossbreeds are healthier overall [see below].  However, “overall” means comparing all purebreds with all mutts and if you compare all mutts with individual breeds, it’s clear that some of the smaller, hardier breeds are healthier.
The same goes for longevity, too. Overall, mutts live – on average – a little longer. In fact, they’re likely to be at our feet for up to two years longer according to one key study. But this doesn’t mean that mutts outlive every breed – they don’t. That’s because small dogs tend to live longer than large ones and that endures across the purebred/crossbreed divide. Some terriers, miniature poodles and whippets live longer than the average cross.  So breeders of these breeds really could justifiably claim that their dogs are healthier than most mutts. But it’s not a very fair comparison because if you split the crosses into size categories, the crossbreed benefit manifests once again. In other words, small crossbreeds live longer than small pedigree dogs (and the same is true for medium and large dogs too).
Insurance company data also confirms the crossbreed health benefit. Most charge lower premiums for crosses and mixed breeds. This isn’t because they’re “anti-pedigree” – an accusation often levied at anyone who dares sing the health-merits of the average mutt. Nope, it’s bottom-line not opinion that cuts ice with the actuaries. They’ve calculated the risks by looking at their data (ie claim history) and priced their premiums accordingly.
For all these reasons, we felt able to say in Pedigree Dogs Exposed that crossbreeds are – overall – healthier than their purebred cousins. Of course this isn’t to say that every mutt enjoys rude good health – they don’t. I wrote recently about losing a lovely collie cross to lymphoma at the age of two and you don’t have to look very far to find crosses suffering from many of the same conditions that blight our purebred dogs. It’s just that, statistically, they’re less likely to be sick. In fact, as I’ve mentioned before, one recent Italian study found that purebred dogs were twice as likely to suffer from cancer than crossbreeds.
“Ah but,” cry responsible breeders, “studies comparing mongrels and purebreds lump all the purebreds together. If you just compared the dogs we breed – carefully selected and fully health-tested – you’d find that our dogs are healthier.”
What the breeders are claiming here is that the disease statistics are being skewed by all those dodgy purebred dogs being produced by backyard breeders and puppy farms.  This sounds plausible, but is there any evidence that it’s true?
No, there isn’t. Actually, there’s next to no evidence to suggest that it isn’t true, either, so the jury is out on this one.  I’ve only found one survey that did the comparison – of Scottish Terriers in America – and it disproves the breeders’ claim. In 2005, Great Scots Magazine did the biggest-ever health survey of Scotties (785 dogs) and found absolutely no difference in disease-rates or longevity between “well-bred” Scotties and others.
“I expected to find statistically verified greater health in the well-bred group,” says Joseph Harvill, publisher of Great Scots Magazine. “That has been the classic claim of show breeders. But I found no significant difference in health benefit between the two groups and it raises real questions to me about the validity of the show breeders' health claims.” In fact, more recent studies by the Scottish Terrier Club of America's Health Trust Fund looking at cancers  - especially bladder cancer from which Scotties are 30 times more like to suffer than other breeds – support the findings. “There is no safety among show dogs,” insists Harvill.
It’s only one study though and you can’t apply the findings across all breeds. It may well be that, in other breeds, show-bred dogs are indeed healthier than the rest of the population. But the show-breeders can’t simply assume this without data to support the claim.
So there we are.  On the evidence we have to date, pedigree dogs can fairly boast predictability of type, looks, character traits and temperament. But in terms of health and average longevity, the humble mutt rules – with the possible exception of working dogs that have been carefully and sometimes ruthlessly bred for fitness and function – a process that in many ways mimics natural selection. Racing greyhounds, for instance, do not suffer from hip dysplasia.
It is the case that not all mixed breeds are created equal. If we breed crosses in the same way as we breed pedigree dogs (as certainly happens with some designer dogs) it’s asking for trouble.  One reason why randomly-bred dogs enjoy a health benefit is that they get to choose their own mates (a process by which nature ensures that only the fittest get to breed). Further, if the individuals dogs are in poor health (genetically or otherwise) and we then go on and inbreed the offspring, we’re on a hiding to nothing.  In other words, just being a crossbreed or mutt is no guarantee of superior health and if a breeder of Labradoodles, Goldenoodles, Cockapoos, Puggles or any other cute mix tries to claim otherwise, vote with your feet and walk away - particularly if they insist there is no need to do any health-tests because their pups will be the automatic beneficiary of hybrid vigour.  It ain’t true.

References (researched and collated by Dr Hellmuth Wachtel):
• B.N. Bonnett, A. Egenvall, P. Olson, A. Hedhammar, Mortality in Swedish dogs: rates and causes of death in various breeds, The Veterinary Record, 1997. ("Mongrels were consistently in the low risk category")
•  P.D. McGreevy & W.F. Nicholas, Some Practical Solutions to Welfare Problems in Pedigree Dog Breeding, Animal Welfare, 1999. ("Hybrids have a far lower chance of exhibiting the disorders that are common with the parental breeds. Their genetic health will be substantially higher.")
• A. Egenvall, B.N. Bonnett, P. Olson, A. Hedhammar. Gender, age, breed and distribution of morbidity and mortality in insured dogs in Sweden during 1995 and 1996, The Veterinary Record, 2000. ("Mongrel dogs are less prone to many diseases then the average purebred dog.")
•  A. R. Michell, Longevity of British breeds of dog and its relationship with sex, size, cardiovascular variables and disease, Veterinary Record, 1999. ("There was a significant correlation between body weight and longevity. Crossbreeds lived longer than average but several pure breeds lived longer than cross breeds, notably Jack Russell, miniature poodles and whippets”.)
• G.J. Patronek, D.J. Walters, L.T. Glickman, Comparative Longevity of Pet Dogs and Humans: Implications for Gerontology Research, Journal of Gerontology, Biological Sciences, 1997. ("The median age at death was 8.5 years for all mixed breed dogs and 6.7 years for all pure breed dogs For each weight group, the age at death of pure breed dogs was significantly less than for mixed breed dogs.")
• H.F. Proschofsky et al, Mortality of purebred and mixed breed dogs in Denmark, Preventive Veterinary Medicine, 2003. (Higher average longevity of mixed breed dogs. Age at death when split into three age bands: mixed breeds 8,11,13, purebreds 6, 10, 12)
• Marta Vascellar et al. Animal tumour registry of two provinces in northern Italy: incidence of spontaneous tumours in dogs and cats. BMC Veterinary Research 2009. (“In both dogs and cats, purebreds had an almost 2-fold higher incidence of malignant tumours than mixed breeds.”)
• Agneta Egenvall et al. Mortality in over 350,000 Insured Swedish Dogs from 1995–2000; Breed-Specific Age and Survival Patterns and Relative Risk for Causes of Death. Acta Veterinaria Scandinavica, 2005. (No difference overall, but mongrels low-risk for locomotor problems and heart disease.)
This article first appeared in the October 2010 issue of Dogs Today Magazine.

38 comments:

  1. I always find it interesting that breeders are so sure of their breeding's health. There is no room for exception with this crew, their dogs are always healthier and that is because they suffer from what we can call the Yogi Bear syndrome, They are "smarter than the average bear".
    That said, breeding is still a crap shoot. You're betting that all the genes passed on in a mating will be free of every major, critical genetic defect. Each puppy get the same chance, 50/50, not the numbers in Mendel's square.

    ReplyDelete
  2. The thing with breeders of the 'doodle' type is that they arent saying they are healthier, they are claiming they are 'non allergenic' and 'dont moult'. This is simply not true, many do moult. Also I know many people who have doodle crosses who are not aware that they need the same coat care as a poodle. These poor things run around in mats and unable to see because of long eye hair. The breeders need to point this out, not just make money!

    ReplyDelete
  3. Hybrid vigour is a myth for one very good reason. You cannot compare the longevity of a great dane against a jack russell terrier, in the same way, you cannot compare a cross breed, that is likely to contain a longer living breed and shorter living breed, against either of the pedigree parents. The issue is far more complex than pedigree vs cross breed. What's the saying, there are lies, damn lies, and statistics??

    ReplyDelete
    Replies
    1. Hybrid vigour is, CATEGORICALLY, not a myth, and you mark yourself as a buffoon when you try to dispute that. This is always a difficult notion to communicate to people who are not familiar with it, but the long and short of it is that this issue is complex, and any blanket statement or sweeping generalization is virtually guaranteed to be wrong.

      Delete
  4. Tarimoor--did you read the article?

    ReplyDelete
  5. Bit curious if people who have spent more on a dog are more likely to take it to receive healthcare, or more expensive care such as surgeries instead of crate rest, than people who have spent less. That could affect the statistics, but how to correct for it is for the trained statisticians.

    ReplyDelete
  6. Kate, I read the article, and it didn't really answer the question.

    ReplyDelete
  7. Tarimoor, I may be dense but why can't you compare a GD with a JRT in terms of longevity?

    ReplyDelete
  8. Insurance company data also confirms the crossbreed health benefit. Most charge lower premiums for crosses and mixed breeds

    The above statement is actually laughable Jemima. I think you need to join a doodle forum.
    Some insurance companies actually charge higher premiums for doodles, and I know of 1 at least that have Doodles on their "dogs not insured list"

    Most doodle owners do not pick the doodle option but choose the crossbred option so how can the statistics be correct Mmmm makes me wonder

    ReplyDelete
  9. Being a primary producer I am constanly amazed that pure bred dog breeders believe that the canine is the only species that hybrid vigour doesnt exist in, yet they make use of this very idea when they bring in a dog from unrelated stock.

    It also find it shocking that cross breeders use hybrid vigour as a selling point for randomly crossbred dogs, an excuse why they dont health test and a reason to use poor quaility brood stock.

    While heterosis is a very valuable tool in the reproduction of any species unless population genetics is understood and applied to dogs we may never see it used to its full advantage.

    ReplyDelete
  10. Mmmm... are you suggesting some kind of conspiracy or agenda, Anon? Yes, of course you are.

    But I don't make statements lightly and the one above is correct - based on checking with several different insurance companies - including the KC's. You'll also note that I qualified it by saying "most charge lower premiums for crosses and mixed breeds" and so you finding an exception doesn't make it wrong.

    You'll also note that I am not referring to named crosses such as Labradoodles.

    If you want to tell me my statements are laughable, Anon, it would be helpful if you could supply some evidence. Could you give me an example of an insurance company that charges higher premiums for doodles? And also which one has doodles on their "dogs not insured list"?

    Just checked with the KC's own health insurance, by the way. Here's what they charge for their top cover for an owner in London:

    Labrador: £71.08 pm
    Standard poodle: £57.03
    Labradoodle: £62.36 (as you might reasonably expect, somehwere between the above two figures)
    Crossbreed: £40.65

    Jemima

    ReplyDelete
  11. Katrina, I dont get it either....they also believe that whilst inbreeding is not a good thing for longterm health in every other species known to mortal man......its fine in dogs. Oh and that population genetics can be used on many small gene pool species.....but dosnt affect dogs apparently.

    And you can explain until you are blue in the face that the laws of science do indeed apply to dogs and im afraid you may as well talk to the wall.
    They have been ignorant for too long and have trained those that follow too well !

    ReplyDelete
  12. This is a great, clear explanation of hybrid vigor, Jemima. Here are two pieces of supporting data. First, a link to the summary of findings from Great Scots Magazine’s 2005 health survey:

    http://www.tartanscottie.com/pages/GSM_2005_Health_Survey_Report_1column.pdf

    And next, an overview of an outcross experiment in the wild that has revived the Florida panther:

    http://www.npr.org/templates/story/story.php?storyId=130078633

    ReplyDelete
  13. Great article. The arguments against "hybrid vigor" are so inane as to disqualify most people making them from walking across the street safely.

    There's no species requirement, nor strain requirement, we are smarter than that. The only thing that needs to be different is the allele for the gene in question.

    The goal is not "hybrid" so much as it is simply heterozygosity. The state of having two different alleles at one gene locus in the offspring. It's the exact opposite of the COI.

    This state renders all recessive diseases harmless (or muted) in the individual. That's the vigor.

    The observation that "you can still have a bad gene in both parents!" in no way negates the benefits of heterozygosity. If both parents are doubled up on a bad recessive and/or carriers, then YES, you can't guarantee that the offspring will be carriers or clear. But this example negates the assumption of heterozygosity!

    When "outcrossing" is still inbreeding, then yes, you will suffer the effects of inbreeding.

    Perfection is not a choice. A breeding scheme does not have to be perfect or a cure all to be BETTER than the current system. Such arguments are childish and ill informed.

    Show breeders spend a lot of effort to get recessive alleles to pair up. It's no wonder they are so against them by nature, and so violently opposed to reason. But gaining hybrid vigor doesn't require you to make radical outcrosses to totally unlike breeds.

    It's just a mathematical certainty that the further you go the more likely you are to find fresh and different alleles when you are otherwise unable to test.

    For instance, Border Collies would risk little in the way of losing recessive conformation genes (structure, coat color, etc) if bred to English Shepherds. So in this respect, it's not much of a "hybrid"-ization. But as far as other genes go, you have a better chance at reclaiming diversity that has been lost over the hundred+ years that the breeds have been separated.

    Humans are very good at breeding out visual phenotypes, but the selective pressures against other hidden genes, like the diversity in immune response genes, are not as strongly selected for or against. Whereas a popular sire in BCs might have made some immune genes rare accidentally, there's a good chance that those same genes weren't accidentally selected against in the English Shepherd.

    The first generation will be totally free from doubling up on any recessive diseases and even later generations will show a marked decrease in expression when bred back BLIND to the original or "hybrid" community.

    If your standard is to breed no disease, then you should never breed a litter of anything. There is no healthy dog, no healthy breed, that does not play host to recessive diseases.

    Our goal as breeders should be to minimize disease, and that's not what's happened. Despite claims that it's some mythical boogey man like "backyard breeders" or "puppy mills" that cause genetic harm, that's not supportable by any facts.

    Dogs with papers are maximized with disease. That's why scientists study them to learn about human disease, you go where the action is.

    None of the Kennel Club breeders can go to their stud books and document where the BYBs and PMs have ruined their breeds and polluted their gene pools.... those canards never make it into the show pools. But I can go to the stud books and show you where popular sires and closed books have lead to increased homozygosity == decreased heterozygosity, meaning highly predictable expression of both recessive physical traits and disease.

    That's the thing with papers. They document the sins of the past and we need look no further to explain why pedigree dogs are a mess.

    ReplyDelete
  14. "While it is true that a lion/tiger cross would produce a hybrid animal," and these crosses called Ligers have been done, and they are infertile!, so much for hybrid vigour if it then cant reproduce!! or do you have a wayof wriggling out of that one too?

    ReplyDelete
  15. I guess I do. The whole blogpost refers to the hybrid vigour that manifests when crossing to unrelated lines within a species, not between them. I made absolutely no claims of hybrid vigour for a liger (only the males are usually infertile, btw, not the females) or any other true hybrid. They are often infertile. Which of course makes the claims from the naysayers that hybrid vigour ONLY manifests inter-species all the more ridiculous.

    ReplyDelete
  16. Anon 03:43, that is a truly idiotic comment. Truly hope that person isn't breeding animals if they have that little understanding of such basic principles.

    ReplyDelete
  17. Anon 03:43. Lions and tigers are quite genetically distinct from each other in ways that dogs are not. They diverged from each other millions of years ago. Closed registry dog breeds have been around-- for the most part- around a hundred years. That's about the time the registries started to close up. But the breeds existed, interbreeding occasionally. If you look at early 20th century golden retriever pedigrees, you find Labradors, flat-coats, and even a few curly-coats. The registry official closed for goldens in 1916, although there were always some crosses that were allowed in "under the radar" or through false papers.

    Dogs are not only interfertile, they produce interfertile wolfdogs, which are crosses with the ancestral wild species. They also produce fertile hybrids with golden jackals, coyotes, and Ethiopian wolves. Not all golden jackal and coyote/dog hybrids are fertile, but many are.

    Ligers and tigons are not always infertile. According to Haldane's Rule, hybrids between different species will have one sex that that is either absent or is always sterile. In the case of Ligers and tigons, the males are always sterile. The females are, too, but, just like mules, a few female ligers have been found to be fertile:

    http://www.forevertigers.com/evolution.htm

    ReplyDelete
  18. I find the comments concerning the health of the designer breeds being so much healthier than pedigrees hilarious. Also the survey taken from the insurance companies equally hilarious, the one I saw did not include any of the well known companies that many dog breeders would use, no doubt someone will argue about that. As regards premiums, I recently received a renewal for my 8 year old rescue cross breed, he has never had a days illness or a claim. It has doubled, when I queried this I was informed cross breeds become unhealthy after 8 years. I also insure 3 pedigrees together and only pay double what I am paying for him. I shopped around and could not get any lower premium for him in fact most were higher again. As regards problems, I was recently at my vets and saw 3 of the so called labradoodles all waiting to be seen, they turned out to be from the same litter, they were 11 months old and all had serious health problems, but not the same, I mentioned this to the vet and was informed another 3 from the same litter were also patients. Where I walk my dogs there are 2 people with cross bred mastiffs, both had OCD at 6 months, both from untested stock and the breeder has another litter of 10 I believe from the same Dam

    ReplyDelete
  19. I am sceptical about what you say re your insurance company saying "crossbreeds become unhealthy after 8 years". This is, indeed, the age at which insurance premiums tend to rise - but for ALL dogs, not just crossbreeds. Perhaps you could tell me the name of your insurance company and I'll check?

    As for the insurance company data - the Swedish research is Agria (huge) and the data used by Michell in his 1999 paper originated from PetPlan, the biggest in the UK.

    Re your 'hilarity' re the designer crossbreeds, did you actually read the final paragraph? It says explicitly: "It is the case that not all mixed breeds are created equal. If we breed crosses in the same way as we breed pedigree dogs (as certainly happens with some designer dogs) it’s asking for trouble. One reason why randomly-bred dogs enjoy a health benefit is that they get to choose their own mates (a process by which nature ensures that only the fittest get to breed). Further, if the individuals dogs are in poor health (genetically or otherwise) and we then go on and inbreed the offspring, we’re on a hiding to nothing. In other words, just being a crossbreed or mutt is no guarantee of superior health and if a breeder of Labradoodles, Goldenoodles, Cockapoos, Puggles or any other cute mix tries to claim otherwise, vote with your feet and walk away - particularly if they insist there is no need to do any health-tests because their pups will be the automatic beneficiary of hybrid vigour. It ain’t true."

    ReplyDelete
  20. Many Labradoodles and the rest tend to be bred from stock that hasn't been tested or anything, so you get these dogs with poor health

    You cannot make comparisons about the health of these dogs from anecdotal evidence.

    There will always be exception to the rule on an individual basis.

    But as a whole, what has been written here is true in the great sense, at the macro level.

    ReplyDelete
  21. The latest BVA figures for the UK, just out, show that in their relatively short existence, a considerable number of labradoodles have been hip-scored - 603 in fact, which is more than many other breeds, known to suffer CHD, have managed in the past 40+ years. In fact, twice as many labradoodles than standard poodles were hip-scored in the UK last year (195 compared to 98). There are undoubtedly some conscientious breeders of labradoodles. Their BMS for 2010 is 13 - compared to 14 for both the labrador and standard poodle.

    ReplyDelete
  22. but just how many labradoodle have been bred in that time and what % come from tested parent?

    ReplyDelete
  23. Labradoodles are a bit of an odd case because at least some of the people breeding them don't appear to understand the distinction between the F1 generation (uniformly half chromosomes from labrador parent and half from poodle) and subsequent generations (which may in fact be inbred if the breeder is trying to "fix" the new type.

    ReplyDelete
  24. lol.. 'randomly bred dogs get to choose their own mates'.. now that is funny.. sort of like 'the bachelor' on tv.. not quite.. you only need to go to the beach in Spain or Mexico and see loose dogs.. each bitch 'choosing' her own mate..this one first.. then that one.. then the tall one.. then the long haired one.. lol.. one of the funniest statements I have ever read on this blog..
    the way to cure the argument about pet insurance costs is to eliminate it..

    ReplyDelete
  25. "the way to cure the argument about pet insurance costs is to eliminate it.."

    I'm curious to know exactly what you mean by this?

    That people shouldn't insure their pets at all?

    Pet insurers have a financial interest in reducing the risk that payouts will exceed the cost of premiums paid. This means that their premium tables are the best source of unbiassed information about breed differences that we have.

    There are limitations - a breed that was prone to something that caused sudden death at low age would be low-risk from the point of view of insurance payouts (the dog's dead so there's no veterinary cost).

    ReplyDelete
  26. "Pet insurers have a financial interest in reducing the risk that payouts will exceed the cost of premiums paid. This means that their premium tables are the best source of unbiassed information about breed differences that we have."


    Not at all, unless you first have to hand quantifiable data for example as to what percentage of each breed is acatually insured and accurate recording of the animals' breeds in in place etc. If in the population of breed X, only 30% of the population are insured, and these are mainly from a particular destination (eg puppies purchased with free insurance from breeders) then it will give a biased sample. Many people may insure a younger dog but as insurance premiums rise as the dog ages, they often cancel the policy. A dog obtained from a rescue centre with no history, might be described as a 'breed Y' and insured as such where in reality it could well only be 3/4 breed Y. Owners with insurance are probably more likely to seek veterinary advice and opt for different treatement to those without. I'm sure there is a difference in insurance take up between different sectors of the population, even different regions of the country. In the commonly puppy farmed breeds, there is no record of whether the animal was bred by a contientious breeder who has made every effort to produce a healthy dog, or bought from a dealer and the product of sickly over bred parents. This can and does make a huge difference. Everyone is in agreement that there are places which churn out sickly puppies yet the source of a dog is not considered relavent when information dependant on vet and insurance data is mentioned. If data from insurance companies isto be used to determine disease prevelance etc, then it needs to be a lot more robust than is currently the case and viewed with considerable caution.

    ReplyDelete
  27. Well that's not what a 2009 paper concluded in 2009 - although not without some caveats, as one might expect.

    http://www.actavetscand.com/content/51/1/42/abstract

    "We conclude that insurance data can and should be used for research purposes in companion animals and horses. Insurance data have been successfully used, e.g. to quantify certain features that may have been hitherto assumed, but unmeasured. Validation of insurance databases is necessary if they are to be used in research. This must include the description of the insured population and an evaluation of the extent to which it represents the source population. Data content and accuracy must be determined over time, including the accuracy/consistency of diagnostic information. Readers must be cautioned as to limitations of the databases and, as always, critically appraise findings and synthesize information with other research. Similar findings from different study designs provide stronger evidence than a sole report. Insurance data can highlight common, expensive and severe conditions that may not be evident from teaching hospital case loads but may be significant burdens on the health of a population."

    ReplyDelete
  28. The abstract appears to confirm what I said, insurance data has limitations in it's current form and findings should be interpreted with caution. For exmple some 'diseases' prevelant in a breed may not even show on insurance records if there is no veterinary treatement possible for the condition.
    However, used IN CONJUNCTION with other studies it could be useful information.

    ReplyDelete
  29. I just found this blog today and I've enjoyed what I read so far. I just got a mutt, probably mostly herding types, from a shelter last October. In answer to the commenter who suggested that people will pay more for the health care of an expensive dog than they will for the inexpensive mutt: whether or not an owner will pay the necessary vet bills depends entirely on the character and financial circumstances of the owner. If you bond with your dog, you're going to take care of your dog and that's all there is to it. I can't conceive of looking at my Sophie and thinking, Sorry, girlie, but you only cost $100 so no doctor for you.

    ReplyDelete
  30. Labradoodle is just another case of outbreeding depression. Hybrid vigor is shown strongest result in F1 and gets weaker after generation to generation. On the contrary, Labradoodle is different because they still shed coat in F1 and F2 generations and then become non-shed until F3. It means that the non-shed coat trait is weak in first generation but the trait increases in power through the further generations. This is, in fact, the characteristic of outbreeding depression.

    ReplyDelete
  31. I'd say you get hybrid vigor . . . sometimes . . . but no guarantee. You can also get health and vigor by careful breeding within a breed.

    Insurance company rates may reflect dog health, but more likely they use breed as indicators of the owner's wealth, willingness to pay, and inclination to make frequent visits to the vet.

    One point difference in hip scores means nothing. If you go to the OFA website you'll find the following average hip scores: hybrid, 19.4; labradoodle, 14; Labrador, 11.9.

    All else equal, heterozygosity is better than homozygosity . . . but when it comes to loci that control genetic diseases, I'll go for homozygous and clear every time. Good pedigree-based breeding will work toward eliminating carriers and ending out with low incidence of disease genes . . . and as genetic testing extends to more defects, our ability to breed out health defects will increase.

    I've owned mutts, and there are some cross breeds I like a lot. But there's a lot to be said for being able to predict what you're going to get, and degree of predictability is higher with pedigree dogs. That's especially true of working dogs . . . you're not going to get a good sheep guardian or soft-mouthed retriever from looking for the pick of the dog pound.

    ReplyDelete
  32. Jennifer wrote:

    "Insurance company rates may reflect dog health, but more likely they use breed as indicators of the owner's wealth, willingness to pay, and inclination to make frequent visits to the vet."

    No, this is not true and this claim always makes me squirm because I think all it really reflects is the claimant's own somewhat racist view of a crossbreed's worth.

    It's a very big assumption that people who have crossbreeds value/love/care for them less and are less likely to take them to the vet if they're sick. Perhaps there was some truth in this in the old days of easy-come/easy-go mutts, but I think this is very rarely true today. There are bad/uncaring/rich or poor owners across the board and, as for value, just look at what some people pay for a designer crossbreed.

    "All else equal, heterozygosity is better than homozygosity . . . but when it comes to loci that control genetic diseases, I'll go for homozygous and clear every time."

    If only genes/alleles were such discrete entities that you can select for homozygosity on just those loci that control genetic disease and for heterozygosity elsewhere. It simply doesn't work like that.

    "...there's a lot to be said for being able to predict what you're going to get, and degree of predictability is higher with pedigree dogs. That's especially true of working dogs . . . you're not going to get a good sheep guardian or soft-mouthed retriever from looking for the pick of the dog pound."

    Of course. But no one is arguing otherwise. I have some fabulous crossbreeds, but none of them could do the job my working flatcoat does. The whole purpose of this blog is to encourage people to change what they're doing - to try to avert the tragedy of there being no flatcoats and other breeds in 50-100 years because they will have become genetically unsustainable.

    Jemima

    ReplyDelete
  33. Jennifer said...

    "All else equal, heterozygosity is better than homozygosity . . . but when it comes to loci that control genetic diseases, I'll go for homozygous and clear every time."

    If only all genetic disease were that simple. You may wish to look up risk factors related to certain DLA genes, especially in the homozygous state. And let me know when you isolate those single recessive alleles for cancer and heart disease.

    Also look up epigenetics and nutrigenomics while you're at it.

    There are a bazillion genetic diseases out there; the ones caused by simple recessives are few and far between. It is a mistake to thing that being clear for a simple recessive means a dog is 'healthy.'

    ReplyDelete
  34. JH wrote: No, this is not true and this claim always makes me squirm because I think all it really reflects is the claimant's own somewhat racist view of a crossbreed's worth.

    Evidence, please. My statement grows out of having MSc in economics and knowing something about how corporations work. I'll admit to racism: I prefer some breeds to others. But I have no objection to miscegeny.

    In my years running a boarding kennel, I think I'd be comfortable saying X-breed owners are a little more down-to-earth than pedigree dog owners . . . less inclined to be hypochondriacs, and generally more capable of dealing with minor problems without going to the vet. ONLY on average . . . lots of exceptions in both directions. Could be wrong.

    I would love to see breeding systems opened up. Eg, I think it's inherently cruel to keep a dog with a duplex coat in a tropical/subtropical climate. You could breed-down the coat for the various breeds by outcrossing and backcrossing and end out keeping the breed essentials . . . less the heavy coat. . . .if it weren't for the kennel clubs.

    I know much more about Lab breed history than other breeds . . . and it's very clear that Labs came to be the wonderful dogs they are by much mixing of breeds and selection of dogs suited to a certain job and a certain lifestyle. It's a shame that this sort of breed evolution has been terminated for most breeds.

    I think un-moderated advocacy of cross breeds plays into the trend to puppy mills breading for pet shops. Out of the frying pan, into the fire.

    ReplyDelete
  35. You mislead here. The Scottie Health survey repeatedly mentioned that there was insufficient evidence/data to conclusively determine health differences between breeder Scotties and others. Also the survey did not break down health issues but instead used broad categories. Would be interesting to know the difference between breeder dogs and other origin dogs with respect to chronic health conditions and structural problems that are not life-threatening. Also many of us love purebred dogs and do not want mixed breeds. Long time breeders are usually very familiar with the health in their line and can use selective breeding to avoid or eliminate known health problems. I'd take a purebred from a responsible breeder over the unknown of a mixed breed any day.

    ReplyDelete
    Replies
    1. "I'd take a purebred from a responsible breeder over the unknown of a mixed breed any day."

      Why? What benefit does it confer to be "pure bred" ?

      Dogs are individuals, there are TENDENCIES in a breed but not all dogs of a breed act or think the same as the TENDENCY. So whenever you get a dog as a puppy you're taking a gamble whether you get a mutt or a "pure bred".

      My rescue Border Collie of unknown parentage is fine with living in a tiny flat in a city, being left alone for 5 hours 5 days a week and only getting off-leash exercise at the weekends.

      My cousin's pure bred, pedigree chihuahua and Bulldog eat the furniture, pee everywhere and bark all day if left for more than a couple of hours.

      Ask most people which breed out of the 3 you'd pick for an apartment and most would say chihuahua or bulldog... definitely not a Border Collie.. and yet my dog has no issues and seems very happy with his situation.

      Clearly despite inbreeding dogs are individuals not clones. You should pick a dog based on its individual character and health and ignore something as superficial as looks.

      That's what I did - despite having a particular bias for mongrels and moggies, when I went to rescue a dog my bc was the only dog that fit my criteria (quiet, calm, focused, biddable, gentle). I couldn't be happier with him. My next dog will be chosen in the same way - I wonder which breed (or mutt) I'll end up with next.

      Delete
  36. I'm only anonymous as I can't log-in join at present ! - but I must say that Tarimoor's early comment is the most stupid argument I have ever heard !!!!!!!!!......talk about blinkered Pure Bred Show World Blood-Lined tosh !!!!!!!!

    Jemima has opened up your world and found a few secrets even a purist dog lover would baulk at !

    No wonder this have all been done "behind closed doors" for so long !!!!!!!

    At least the Ethical Breeder is what the Public will choose and more awareness such as this will allow the Public voice to get louder and as such Puppy Farms et al will reel !

    Breeding Ethics !!!!!!!!!!!! and it's not always for Pounds - it can be done for Passion !!!!

    CC x

    ReplyDelete