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.