Monday, July 16, 2018

Pedigree Dogs Not as Healthy as Mutts & Mixes

In a comment to an earlier post, a reader writes to suggest that one reason folks may think mutts are healthier than pedigree dogs is "because vets don't attribute specific problems to their breeding - how could they? It's a mix!"

An interesting point, but actually, that's not the reason.

We think mutts are healthier than pure-breeds because they actually are healthier!

And the research, as I noted in an earlier post entitled Pet Insurance Data Shows Mutts ARE Healthier!, is not closely held.

When it comes to warranties and insurance, predictive values are important, and fortunes are made by determining the correct digits to place to the right of a point mark.

What does this have to do with dogs?

Quite a lot.

You see, pet insurance companies are in a competitive business to get your dollar. If they get the numbers wrong, and price a premium too high, potential customers may forgo pet insurance altogether or else sign up with a competitor's plan. On the other hand, if the company routinely prices insurance premiums too low, they may push themselves into bankruptcy.

And so, pet insurance companies have collected data on hundreds of thousands of dogs and analyzed that data, in order to assign correct premiums to predictive risks.

And what do the insurance records show? As I note, by way of example:

Embrace Pet Insurance... will insure a mixed breed dog up to 8 years of age, but the cut-off for purebred dogs is 6 years.

What's that about?

Simple: Taken as a whole, there is a "health gap" between cross-bred and pedigree dogs, and that gap is about two years. The insurance industry is simply mirroring in policy, what has been proven true on the ground.

Of course, there is more data. Over at the Cold Wet Nose blog, Beverley Cuddy has put up some of the citations from Jemima Harrison's current piece in Dogs Today which reviews some of the literature. Citations, with a summary "kicker" quote line to encapsulate the piece, follow:

  • 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 two-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.)

Of course, not all pure breed dogs are a complete mess, and not all mongrels or mixes are the picture of health. "Hybrid vigor" does not quite live up to its hype either. Mix two genetic messes, and you may not get gold out of the opposite side.

That said, all things being equal, mongrels and mixes ARE healthier than pure breeds. Fancy that! And yes, the pun is intended.


Seahorse said...

"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.”

Yea, us!


Jess said...

There are a large number of studies on Pubmed where being a mixed breed is considered protective against the disease in question. It does not take much effort to find them.

seeker said...

Yes, Seahorse, yea us!

The JRTCA has strict guidelines that shows how serious they are. Here's the link for those who don't know.

The JRs registry is so strict to prevent the AKC fiasco of horrific problems in their dogs. I wish all clubs would do this. Of course, over half the AKC breeders would be out of business.

And even my rescue dogs can be recorded so they can participate in the trials. It's the best of both worlds. Responsible reporduction and enjoyable participation.

Debi and the Texas JRTs.

Stoutheartedhounds said...

In my opinion, inbreeding does not generally do a service to the breed that I work with (greyhounds), and based on my experience with greyhounds I tend to apply that opinion to other breeds as well. However, I came across the website of Diane Jessup, a woman that breeds working pit bulls, and she is a strong advocate of inbreeding. I am hesitant to agree with her because of the fact that inbreeding doesn't work so well with greyhounds, but I wanted to hear what you thought about it, since she backs up her claim with the idea that outcrossing produces inconsistent temperaments (which supposedly is bad for a working pit bull). Based on what I know to be true about producing suitable temperaments in running/hunting dogs, her claim seems a bit unfounded, but I'm willing to stand corrected if there's a significant difference between pit bulls and other guardian breeds and hunting dogs.

PBurns said...

Stoutheartedhounds --

You are right to eschew inbreeding. In fact, you can predict the FAILURE of racing dogs and racing horses by the amount of inbreeding they have -- one reason Coefficients of Inbreeding are tracked so closely in both groups. See >> for a little more information on this.

As for working Pit Bulls, what kind of work does Ms. Jessup have in mind?

You see, a working Pit Bull is not a "Pet Bull." It has a drive and a speed, and a purpose in life which may not make it the best dog for a suburban household with two kids and a small dog and a parrot.

Just saying.....

True working dogs -- dogs that are chasing pigs in Texas hill country, Louisiana swamps, on the side of Hawiian volcanoes and in Australian bush, are almost all cross-bred dogs.

In fact, a Pit Bull is not really a breed at all, but a broad TYPE of molosser, just as a Jack Russell terrier is a broad type of terrier.

A Pit Bull, in short, is any dog that looks like a Pit Bull, just as a Jack Russell is any dog that looks like a Jack Russell.

And YES, it is a broad standard, not a narrow one.

As for the notion that you get better personalities from pure breeds, time and experience has shown that it's simply not true.

Ever hear of a guy by the name of John Paul Scott? In the 1950s, he worked at Jackson Labs and is most famous for doing the puppy socialization experiments in the 1950s with five breeds over 16 weeks that showed that dogs do best if they stay with their mom for 8 weeks.

In the early 1990s, Scott was an advisory board member of the Assistance Dogs Institute in California and he said that temperament and health in pedigree dogs had deteriorated to the point that it was time for the service dog industry to do what cattle men and women had started to do 100 years earlier: move to cross breeds.

He wrote: "It's wiser to breed golden retrievers and Labradors with one another and their progeny be used for assistance work (as service dogs to those with visually impaired or with physical limitations) rather than purebred puppies.... This solution doesn't threaten the future of using pure bred dogs for assistance work. Purebred dogs are still required to create these first generation hybrids."

Scott's rationale was that the cost of treating the health problems of purebred service dogs was so high that many of their owners simply could not afford the expense, and that the temperament problems he was also seeing in pedigree dogs was also a growing issue and needed to be addressed.

What was needed were calm biddable dogs, not dogs that merely looked good.

Nearly ten years later, the service dog world is doing what Scott predicted and moving to crosses like the Labradoodle.

Are Pit Bulls "the exception that proves the rule"?


There's no question that there are some folks who are trying to breed dogs that are harder, with more drive, and with less tolerance for other dogs.

But are these folks actually competent at their task, and are there really that many of them?

I doubt it.

Most of the Pitbulls running around in America today are cross-bred dogs of uncertain pedigree, unknown origin, and liberally salted with "Pet Bull" bloodlines.

In fact, I would rather have a backyard-bred dog of "pedigree unknown" than a dog from some of the "pure bred" kennels that are cranking out fighting dog lines.

Look up Pit Bull Kennels and you will find place after place bragging about a fighting dog pedigree or name, whether that is Boudreaux, McCoy, Jeep or Chinaman.

So no, I'm not sure I entirely agree that "Working Pit Bulls" (whatever that is) are going to be improved by inbreeding. They may be improved by more SELECTIVE breeding, but not by inbreeding. And there is a BIG difference between these two terms!


Jennifer said...

I'm not questioning the main point... selective breeding, with selection for breed standard, does not favor health. Especially if the breed standard is freakish.
However, two things stand out in that reference list.
1. The study with the largest N, the Swedish study, concluded:"No difference overall, but mongrels low-risk for locomotor problems and heart disease.". No surprise there. A few breeds, like Dobes and Cavs, have very high incidence of heart problems. Relatively few mutts are giants or freaks...the groups with high incidence of locomotory problems. My bet is that throwing out a few outlier breeds would even the scores.
2. Most of the studies are pretty old. Surely there's been some work on this issue in the last decade.