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Breeding better dogs: a Cavalier attitude
By Kim Campbell Thornton
March 22, 2009
I’ve been thinking a lot about Darcy lately. Week before last, I spent nearly an hour on the phone with the relative of a friend, plus follow-up e-mails. She’s interested in getting a Cavalier, so Janine suggested she talk to me. We talked puppy mills and finding a good breeder, grooming and shedding, exercise (hiking, yes; chasing seagulls at the beach, definitely; jogging, probably not).
Of course, the matter of their health came up. It’s hard for me to know what to tell people about Cavalier health. One of the reasons I liked them when I first chose the breed was because they were small but sturdy. Along with the Pug, they’re the largest of the toy breeds, with a weight range of 13 to 18 pounds–and some are a bit bigger. So they’re not fragile at all.
But there are a lot of health problems associated with the breed: mitral valve disease, syringomyelia, allergies, corneal dystrophy, weirdly low numbers of platelets (which don’t appear to cause a problem), and quite a few other conditions to varying degrees. Not every Cavalier will get all of these diseases and some won’t get any. They may get MVD or syringo and be affected only mildly, finally dying of old age. Or not. It’s a crap shoot.
That’s hard, especially when you’re not a gambler by nature. You won’t find me at the tables in Vegas, and my math skills are not suited to card counting or to genetic calculations. Every day I wonder whether and when it will all go to pieces. Whether I’m doing everything I can to ensure the best outcome. But I love the breed and I can’t imagine living without them, so I go on.
I’ve had four now, and I suppose you could say I’ve had a 75 percent success rate. The youngest seems to be starting off right. The oldest, who I frankly did not expect to still have at the ripe old age of 13, is chugging along quite nicely, thank you very much (with a little help from a couple of pharmaceutical friends) and until she slowed down the past year or two was the most athletic of them all. The one who’s nineish, whose background I don’t know, is in fine shape so far, with only a soft murmur. And then there was Darcy, from a reputable breeder, who was dead at six and a half.
Losing a dog to a breed-related disease is heartbreaking. But even if you’re not a breeder, it’s a powerful incentive to make things better. I talk to people about the breed–the pros and the cons. I write articles about what to look for in a breeder, what health certifications to demand, what’s necessary to be an informed and discriminating puppy buyer. I promote the Darcy Fund to help bring about improvements in health. Some day I may even follow Gina’s lead and breed a litter, if Harper or some other puppy has qualities that should be passed on. In breeds like Cavaliers, with limited gene pools, more diversity may be our only salvation.
I know from experience that no matter what I do, I’m unlikely to reach or persuade large numbers of people. But the ones I do reach are a start. And they’ll share their experiences and spread the word. Biology tells us that seemingly insignificant mutations can add up to significant change. Evolution is slow, but it happens.
(Image: Anything but fragile, visiting Cavalier Chase mixes it up with Gina’s flat-coated retrievers, Christmas 2005)
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Thanks for this post and for being upfront about the issues that Cavs can face. With this sweet breed becoming more popular by the day, you see more and more puppies being born from parents that should have never been bred in the first place.
I agree that discussion of ethical breeding practices and choosing breeders that are out there working to improve their lines is the way to go to combat these problems.
Comment by Dog Guy — March 22, 2009 @ 8:08 am
Great post, Kim. Kim has been trying to lure me over to the Cav side for quite a while, ever since I fell head over heels with one of her delightful girls. The cardiac issues have always given me pause. With responsible breeding, there’s hope that this terrific breed will get healthier.
Comment by Phyllis DeGioia — March 23, 2009 @ 5:16 am
I disagree - I think that there are many other breeds - and mixed breeds out there who provide that same fabulous personality without the crippling, often fatal health issues that plague this breed. Yes, they are the cute, adorable, and hard to resist. But as a breed that was created simply to satisfy someone’s whim to have a dog that looked a certain way, it’s high time there were drastic measures taken to solve their issues - or allow them to humanely go the way of the dinosaur.
Comment by Kim — March 23, 2009 @ 5:17 am
Kim, do you apply this same logic to all dog breeds? If not, why not?
Comment by The OTHER Pat — March 23, 2009 @ 5:52 am
Kim: The evidence suggests that the dinosaur did not go humanely.
I’m still waiting for the proof that “hypbrid vigor” exists.
Comment by EmilyS — March 23, 2009 @ 8:17 am
Emily-Pat - The statistics on the number of Cavs with heart defects are astounding. Bernese are another one to be avoided at all costs, and Dogue de Bordeaux rarely live past six.
Sorry, but when you can define a breed by its lifespan…
And hybrid vigor is a genetic fact. A closed gene pool reduces health and longevity. Period.
Not sure exactly what your dinosaur comment is supposed to mean. Are you suggesting that we re-create little dinosaurs to satisfy people`s whims for the next interesting pocket pet, and then breed them from closed stud books with known genetic disorders…
Comment by Kim — March 24, 2009 @ 4:44 am
I guess it is that you seem to be saying that it is okay to let some breeds fade out of existence based on the fact that they were created to satisfy a human need. Given the fact that you can say that about pretty much ALL breeds to a greater or lesser extent, it had me wondering which breeds you felt had “earned the right to survive” and which had not? Within your worldview, do the breeds with problems get to work at pulling themselves out of the pit, or do they just get discarded because they’ve failed at some set of criteria? And all that said, where do you draw the line at which breeds are permitted to succeed and which ones should be doomed to oblivion?
Comment by The OTHER Pat — March 24, 2009 @ 5:13 am
Kim, just asserting that “hybrid vigor is a fact. Period” does not make it so.
Point me to some scientific studies that mixed breed dogs have fewer health problems and live longer than purebred dogs do.
Comment by EmilyS — March 24, 2009 @ 7:36 am
Kim, the reason I am still willing to gamble on the Cavalier is because I know, or know of, many of them who live long lives without any problem. Yes, statistics say that by the age of 10, 90 percent of Cavaliers have a heart murmur, but 1, a heart murmur is not the same as severe MVD, and 2, heart murmurs become common in many dogs as they age, and that includes mixed breeds.
Comment by Kim Thornton — March 24, 2009 @ 9:08 am
Hybrid vigor IS a fact. It’s one of the primary bases of the modern food supply. Inbreeding depression is the other side of it.
Okay, you want specific data on purebred v. mixed-breed dogs served to you with a linen napkin. Here you are:
http://veterinaryrecord.bvapub.....145/22/625
http://biomed.gerontologyjourn...../52/3/B171
http://www.labmeeting.com/pape.....in-denmark
You are welcome.
Comment by H. Houlahan — March 24, 2009 @ 11:14 am
Heather, those links say that mixed breeds live longer than purebred dogs on average, but that a number of breeds have average life spans longer than mixed breeds.
They don’t, though, happen to be the breeds you favor.
There is one area, though, where there is good science saying that the mere fact of mixing genes contributes to better health, is in the area of immunology. You’ll have a better, more robust, more flexible immune system if your parents brought with them to the mating significantly different immune system alleles. That by itself could contribute to mixed breed dogs having slightly longer lifespans than purebred dogs of the same weight class.
Otherwise, though, the key question appears to be whether or not the geneset is a healthy geneset. If neither parent carries genes for PRA, for instance, the pups won’t have the genes for PRA, no matter how closely related the parents are. The same is true of other, nastier, genetically carried diseases: if the genes are not present, they are not present, and they do not become present merely because the parents are closely related.
Inbreeding reduces the flexibility and robustness of the immune system. It increases the risk of concentrating bad recessives in a given line IF they are present to begin with—but it doesn’t by itself create bad genes.
Most of the current serious problems WRT genetically carried diseases dates from the latter part of the 19th/first part of the 20th centuries, when older empirical methods of screening for healthy breeding stock fell by the wayside in the pursuit, yes, of Purity and other unhealthy ideas, and the tools we have now were not yet available.
Comment by Lis — March 24, 2009 @ 11:55 am
Hybrid vigor is called heterosis in biology and is a very well documented fact. There is a mountain of evidence for it in the animal sciences. Here’s a good place to start for an overview:
http://en.wikipedia.org/wiki/Heterosis
Google Scholar finds about 80,000 matches for heterosis, so there’s plenty more out there.
There is a considerable amount of evidence indicating that dog populations experience both hybrid vigor at low COIs and inbreeding depression at higher COIs. I posted a 4 page summary about this to the Canine-Genetics list this morning. I don’t think it will fit here as a blog comment.
Comment by LauraS — March 24, 2009 @ 12:25 pm
HHoulihan, if that’s the best you can do, then you haven’t proved your case that mixed breeds are healthier than purebreds. In the studies you link, SOME mixed breeds lived somewhat longer lives than SOME purebreds. As reported by owners…..
Laura, I am not disputing “hybrid vigor” as a biological concept; do you dispute “outbreeding depression” (referenced in your Wiki source?)
I’m looking for proof that it exists in dogs, particularly as a generic statement which is how the purebred-bashers use it (all purebred dogs are unhealthier and have shorter lives than all mixed breed dogs).
Comment by EmilyS — March 24, 2009 @ 12:47 pm
An example of outbreeding depression would be mixing a Standard Poodle with a working line German Shepherd Dog, and expecting to get police service dogs from the progeny. Not happening. The progeny might be healthier and live longer than either parent, owing to heterosis. They might make fine pets for some people.
Comment by LauraS — March 24, 2009 @ 12:56 pm
EmilyS, after being given exactly what she demanded, states:
In the studies you link, SOME mixed breeds lived somewhat longer lives than SOME purebreds. As reported by owners…..
Yes, in two of the studies which were not specifically controlled for body size, some small breeds had longer lives than the study population of all mongrels — which are going to be disproportionately medium-to-large dogs in most communities.
A full year of life is insignificant in the size-controlled study. What’s an extra year with a beloved pet, anyway? Why, nothing, not worth considering.
Therefore, purebred dogs, especially highly inbred breeds with effective population sizes in the double digits, are healthier, and the scientific evidence for heterosis in all species, and the widespread use that agriculture makes of this principle, are all imaginary.
Fine. I give up. You win. Biological science does not apply to canis lupus familiaris. Population genetics is the same as creation science and the flat earth. The AKC and closed registry practices are an unqualified success, and have created Methuselah dogs who are so genetically perfect they will never die.
Comment by H. Houlahan — March 24, 2009 @ 1:38 pm
No one here has said “all purebred dogs are unhealthier and have shorter lives than all mixed breed dogs”. That is a strawman argument. The findings from a number of studies are:
- mixed breed dogs are, on average, healthier than purebred dogs
- mixed breed dogs are, on average, longer lived than purebred dogs
- purebred dogs with lower COIs live longer, on average, than members of the same breed that have higher COIs
- many working / performance dog breeders practice inbreeding avoidance to such a large degree that it keeps population COIs low. The same is not true of many show dog populations.
The specific purebred dog populations that match or exceed mixed breed dog longevity are significantly smaller than average in size. Small size in dogs correlates with an increase in longevity. Inbreeding depression / heterosis are not the only genetic factors that influence longevity in dogs, but they are important factors.
If you would like to see evidence of inbreeding depression in purebred dog populations, email me via laura @ saveourdogs dot net and I will send you a summary.
Comment by LauraS — March 24, 2009 @ 2:09 pm
Sometimes I feel like a biiiigggggg cleansing breath and a long walk with actual dogs rather than a debate over theorectical ones.
This is one of those days.
Carry on.
Comment by Gina Spadafori — March 24, 2009 @ 4:28 pm
Gina, I hear you. I walked everyone and then took the pup to my friends business to just hang and socialize.
I’m on week three of my search for a healthy, tested outcross to a line with good longevity… I’m at the point that I am just going to work the dogs, play with them and the kids and hope for inspiration and perspective from the simpler, more practical side of life. :-D
Comment by JenniferJ — March 24, 2009 @ 8:54 pm
A long walk with a breed that suffers a devastating rate of cancer due to high COI… no?
Don’t get me wrong - I’m not suggesting the extinction of breeds here (um, I was NOT the one who brought up the still unexplained example of the dinosaur - still trying to figure that one out…) but I am simply pointing out that maintaining popularity of a breed that is overly prone to genetic defect (and honestly, arguing that 90% of CKCS will have heart murmurs is somehow ok does not bode well for your argument) but rather pointing out it’s about time people were HONEST about what each breed entails.
And to argue that hybrid vigor does not exist… the only thing I can say in response to that is that I suggest you do some research on your topic before arguing such a point. There’s a reason that livestock farmers routinely outcross their stock - there’s a reason that humans don’t marry within their family… no, perhaps those two theoretical dogs posed above will not present PRA… but what other genetic disasters have you just doubled down genes for?
Oh, and as for the poodle/shepherd cross - how about crossing out to malinois, hovawarts, rottweilers, herding breeds - why does it have to be only one dog? Some of the best working dogs I know are carefully bred combinations of several individuals, bred for type and ability, not for breed.
But you’re not talking about working dogs - you’re talking about a dog who looks a certain way.
Comment by Kim — March 26, 2009 @ 6:49 am
I wouldn’t be so sure about the inbreeding. Here’s Woody’s.
McKenzie is about as far an outcross as you can get and still register a dog. Here’s her dad, one of the best hunting retrievers in Scandinavia. Her mom flew from Texas to meet him, and she’s no slouch either: Field-trial placed, agility titled and a bench champion. Again, the dogs are as unrelated as is possible under the current system*.
Now, about the matter of working dogs. I’m all for them. But …
99.99 percent of the dogs in this country don’t have jobs other than to be companions. How can we get better health and temperaments on those dogs, and still have small spaniels, large retrievers, deerhounds, etc. ? To me, that’s the real challenge.
*NO, I don’t think the current system — a closed registry — is optimal. But I’m a reform from within kind of person, not a throw it all out and start over type.
Comment by Gina Spadafori — March 26, 2009 @ 8:15 am
so LauraS: if you crossed a bulldog with a Great Dane, you’d have a dog with “hybrid vigor”, right? And it would be healthy and live a long time? Or, all those new designer breeds.. do they display “hybid vigor”? They should, according to your belief. (BTW Kim, go back and read your original post: YOU brought up the dinosaur, so you’ll need to figure out your own intent)
Come on: Hybrid vigor as an evolutionary factor is irrelevant to domestic pets. Hybrid vigor in animal husbandry is still about choosing the particular animals to breed. “Mutts” are randomly bred. NOT the same thing.
Pretending that it is, and claiming the studies prove things that they don’t, doesn’t change the reality that there is no science behind the claim that mixed breeds are generally healthier than purebreds. (of course SOME mixed breed individuals are healthier than SOME purebred individuals and of course too many show dogs are bred only for appearance)
Show me a REAL scientific study, with proper controls and techniques (something other than “owner surveys” for example), and you might convince me.
For example, you could do a study comparing the OFA scores of registered Labs with Lab-x mixes. Do you think the scores of the mixes would be better? Or you could round up a bunch dogs that have been feral for multiple generations and see if they are “healthier”.. just be sure your measurements of “health” aren’t influenced by variables such as nutrition or environment.
Until then, the issue is as much about the (proper) obsession of purebred dog breeders with the health of their dogs. How many owners of mixed breed dogs even KNOW about health tests like CERF, OFA, Pennhip, etc etc?
Comment by EmilyS — March 26, 2009 @ 8:56 am
so LauraS: if you crossed a bulldog with a Great Dane, you’d have a dog with “hybrid vigor”, right? And it would be healthy and live a long time
Possibly.
This is about odds. There are no guarantees.
Crossing two very short-lived breeds like a Great Dane and a Bulldog is not likely to yield a long-lived dog. But the odds are good that the progeny will live longer than either parent — which in this case isn’t saying much.
Or, all those new designer breeds.. do they display “hybid vigor”? They should, according to your belief.
In the F1 generation, these crosses are likely to live longer than the parents. But breeders who then go on to do F1xF1 and subsequent crosses can lose the hybrid vigor.
Come on: Hybrid vigor as an evolutionary factor is irrelevant to domestic pets.
There is evidence of widespread inbreeding depression in purebred dogs, as well as the converse of hybrid vigor in both mixed breed dogs and in purebred dogs that have very low inbreeding coefficients.
Pretending that it is, and claiming the studies prove things that they don’t, doesn’t change the reality that there is no science behind the claim that mixed breeds are generally healthier than purebreds. (of course SOME mixed breed individuals are healthier than SOME purebred individuals and of course too many show dogs are bred only for appearance)
Look, don’t lecture me about science when you have displayed a profound lack of knowledge about how science works.
You have repeatedly tossed around words like “proof” and “prove” in a discussion that involves findings from science. There is no way to “prove” or provide “proof” of a scientific theory. Science has data, evidence, hypothesis, theories, etc… but not “proof”. If you want “proof”, stick with mathematics.
I offered to send you a summary of studies showing evidence of inbreeding depression and hybrid vigor in dogs, and I posted my email address here so you could contact me. You have not done so. Science requires objectivity.
Yet you continue to post nonsensical statements here that there is “no science” behind the evidence you will not even look at, or that it doesn’t “prove” anything.
Show me a REAL scientific study, with proper controls and techniques (something other than “owner surveys” for example), and you might convince me.
Science consists of more than just controlled randomized prospective research studies. The science of epidemiology relies heavily on retrospective studies, including survey results.
I’m sure that Professor Glickman, Section Head of Clinical Epidemiology at Purdue University’s School of Veterinary Medicine, might be surprised to learn that a scientific study based on a survey of dog owners isn’t a “REAL scientific study.” Dr. Glickman has been involved in a number of scientific studies of dog breed health that are based on owner survey data. And while Dr. Glickman is among the most prominent veterinary research scientists who has done so, he is certainly not the only one.
Professor John Armstrong of the University of Ottawa, who founded the Canine Diversity Project, also relied on “owner survey” data for his scientific studies of dogs.
Many “REAL scientific studies” based on owner survey data have been published in peer-reviewed veterinary medical research journals. For example, the scientific study that’s been mentioned on this blog which found that 1 in 4 Rotties s/n before 12 mo. of age end up getting bone cancer? That was from owner survey data.
Comment by LauraS — March 26, 2009 @ 12:12 pm
You know how it seems that often you hear of some study that says (fictitious example) “Eating more grapes reduces cancer” and then not too many years later there’s another study that comes out with “no evidence that increased grape consumption related to decreased cancer rates” or maybe “Too many grapes leads to heart disease” - you get the idea.
The first study peeps will say the new study is faulty, someone else will say a 3rd study is needed over a longer period of time, etc. I am often left thinking “I don’t know WHAT to believe”.
I’m no science-hater but as I get older, I find myself feeling more confident in my “common sense” and “experience” conclusions. Know what I mean?
Comment by YesBiscuit! — March 26, 2009 @ 12:44 pm
I’m no science-hater but as I get older, I find myself feeling more confident in my “common sense” and “experience” conclusions. Know what I mean?
Not always, but oftentimes those conflicting findings from different scientific studies are greatly exaggerated by the mainstream news media. [Witness the widely-reported fairy tale alleging no consensus among climate scientists about global warming]. Most news reporters appear to be so scientifically-illiterate they cannot accurately report scientific findings.
I appreciate your frustration. “Common sense” and “experience” are wonderful. But if we rely only on those, and turn our backs on science, we will have basically set the clock back to the Dark Ages.
Comment by LauraS — March 26, 2009 @ 2:20 pm
Gina - I wasn’t intending on taking a stab at your babygirl’s breeding. I understand what went into her testing, training, the choosing of a sire, etc. I also know that as a woman who relies on science and fact, I’m sure you would support a scientifically based outcrossing program to decrease COI’s across the board among all breeds.
My point was not to discourage the breeding of “breeds” period - but it used to be that one bred for type, not for “purity” or for looks. The border collie or JRT are perfect examples, and there are good reasons their parent breed clubs fought long and hard to NOT allow them into kennel club closed registry systems.
Even the Cavalier was originally prevented AKC certification by its parent club due to the fact that the AKC would not abide by their simple code of ethics - including refusing to register dogs who come from puppy mills or commercial breeders. What was once a wonderful dog (and still is, by nature) is now a genetic train wreck. If left to their own devices, they would go extinct - it’s only the monumental effort of veterinarians and owners that keeps the breeds’ longevity even close to where it is.
A quote from terriermandotcom.blogspot.com:
The American College of Veterinary Radiology is set to publish a new paper on The Morphology of the Caudal Fossa in Cavalier King Charles Spaniels.
Not exactly a page-turner of a title, is it?
That said, here’s what the study shows: Out of 64 dogs examined, 59 had morphologic abnormalities of the craniocervical junction, 27 dogs had syringohydromyelia, and 15 presented with clinical signs of syringomyelia.
Ummm… when you can identify a breed by a description of the genetic defects that affect it… shouldn’t something be done?
I apologize if I’ve offended anyone - I understand as well as anyone what it’s like to watch your beloved breed (my own is the Golden - of which I will never again own another) fall into complete genetic disaster. But I make a point of shouting their problems from the rooftops - not touting their virtues. Until the demand for these less than healthy animals falls, there is no reason for a mass movement of breeders towards action that will possibly save their breed.
As for the dinosaurs - there must be some awfully smart cookies on here, given the expert’s lack of ability to determine a cause for extinction, let along its level of humanity… with that notion in mind, do you find the intentional breeding of dogs with the above quoted statistics humane?
Sorry, but I can’t.
Comment by Kim — March 27, 2009 @ 6:40 pm
I think it’s perfectly legitimate to ask the questions … even about my dogs. I surely have asked the questions myself … and not liked all the answers.
But I liked enough of the answers to believe I was going forward ethically and responsibly, at least within the restrictions of the current AKC system, which I believe is in desperate need of reform.
Did you notice that you don’t have to go far back on those Scandinavian pedigrees to come up with “not known”? That’s actually a pretty good thing, and suggests perhaps some breeding of retrievers who proved themselves with their work … and perhaps weren’t even — gasp! — purebred flatcoats.
But hey, all is duly registered and approved by the powers that be. Huzzah.
Comment by Gina Spadafori — March 27, 2009 @ 7:06 pm
We have a lot of those unknowns in ES pedigrees, too.
The problem is, that’s all they are — unknown.
Could be a good thing, could be a bad thing, could depend on what you plan to do with the dog.
We can’t compute meaningful COI’s on most dogs because there are too few complete 7-generation pedigrees, much less more extensive ones.
My main worry with bare branches on the family tree is that they conceal inbreeding — either inbreeding already in a given dog’s ancestry, or the fact that a mate choice is about to be an overly-close pairing.
Of course, the difference may lie in the history of bringing in unregistered dogs to the registered population, which has been common, and continues to this day — transparently and rationally with the breed club registry, and apparently whimsically with the commercial registries.
So we frequently KNOW about the unregistered dogs, and the ones (such as an ancestor of all of mine) that were other breeds. Since we don’t have to “sneak” to expand our breed’s gene pool, we’re more inclined to worry about blanks in the pedigree — a lack of information is just that, not a possibility of salutary “cheating.”
Also, at least one of the commercial registries keeps pedigrees a closely-guarded secret. “Unknown” does not necessarily mean “nobody knows or can ever find out.” It may mean “The commercial registry owner won’t tell.”
And finally, the recent history of the re-assessment of assumed paternity via DNA testing, and the results thereof, suggest that older pedigree data has a high probability of including one or two percent honest errors, fraud, and general bunk. Mostly the first.
Comment by H. Houlahan — March 27, 2009 @ 11:39 pm