Friday, February 14, 2014

The Emperor's New Study

The Emperor's New Clothes Study

Hear ye, hear ye!

New study proves (beyond the shadow of a doubt) that:

Purebred Dogs are Just as Healthy as Mixed Breed Dogs!

Carry on with the mission! Inbreed; linebreed! It's not a problem! Breed to the most popular sire, so you too can have a chance to prevail supreme in the jousting tournament of dog superiority!

We are advocates for health testing, but we don't worry about the risks of narrowed gene pools! That would simpy be too upsetting to the apple cart!

Today I read an article about how AKC wants to "clarify misconceptions about purebred dogs." (a) For one of those "misconceptions" the author cites a recent study comparing the health of purebred vs. mixed breed dogs. The author claims that this study affirms that purebred dogs are just as healthy as mixed breed dogs. 

In actuality, the UC Davis study shows that for heritable health problems common to most dogs, mixed breeds are just as susceptible as purebred dogs, while for many more breed-specific health problems, purebred dogs are more susceptible than mixed breed dogs. This "news" should not come as a surprise to anyone familiar with the science of inheritance and genetics.

However, this same study is continually touted in social media sites and in news releases from the AKC, as some sort of ultimate proof of the undisputed superior health of purebred dogs. Similar to other "Big Lies", there's a belief that if something is shouted loudly enough, everyone will believe it!

Well, not quite EVERYONE. In fact, the American Veterinary Medical Association examined that same study and came to the exact OPPOSITE conclusion:


"The researchers concluded that modern purebred dogs or members of similar lineages appeared to be more susceptible to certain inherited disorders. Disorders occurring equally among purebreds and mixed-breeds suggested that the disorders represented more ancient mutations and were more widely disseminated throughout the canine population." (1)

And the conclusion itself on the published study on Pub Med states:

Recently derived breeds or those from similar lineages appeared to be more susceptible to certain disorders that affect all closely related purebred dogs, whereas disorders with equal prevalence in the 2 populations suggested that those disorders represented more ancient mutations that are widely spread through the dog population. Results provided insight on how breeding practices may reduce prevalence of a disorder. (2)

But, unfortunately, the results did NOT help the willfully ignorant to understand "how breeding practices may reduce the prevalence of a disorder."


Here is a list of a few of the most egregious examples of breed-specific health problems:
  • Purine metabolism dysfunction gene in all (except pointer backcross) Dalmatians
  • Protein malabsorption disorder in virtually all Norwegian Lundehunds ("Lundehund syndrome")
  • Syringomyelia and Mitral valve disease in the vast majority of Cavalier King Charles Spaniels
  • "Collie Eye Anomaly" in Collies and related breeds
  • Copper toxicosis in Bedlington Terriers
  • Fanconi Syndrome in Basenjis

Ah, but we can test and remove dogs with such bad genes from the genepool, right? Actually, that's how Fanconi syndrome became so prevalent in Basenjis. The Basenji breeders noticed a problem with hemolytic anemia. In attempting to eliminate hemolytic anemia, entire families of dogs were culled. Yes, the incidence of hemolytic anemia dropped, but they found many of their dogs were now afflicted with a fatal kidney disease, Fanconi syndrome. They had to return to Africa to add new stock to the decimated gene pool. 

And, according to geophysicist and canine genetics expert Sue Bowling:
“Unfortunately, we cannot breed animals based on a single gene – the genes come as a package. We may inbreed and rigorously remove pups with PRA or even their parents and littermates from the breeding pool. But remember inbreeding tends to make all genes more homozygous. In at least one breed, an effort to remove the PRA-causing gene resulted in the surfacing of a completely different and previously unsuspected health problem. It is easier and faster to lose genes (sometimes very desirable genes) from the breeding pool when inbreeding is practiced than when a more open breeding system is used. In other words, inbreeding will tend to produce more nearly homozygous animals, but generally some of the homozygous pairs will be "good" and others will be ‘bad’.....Furthermore, there may be genes where heterozygosity is an advantage……A more widespread case is the so-called major histocompatibility complex (MHC), a group of genes where heterozygosity seems to improve disease resistance.” (3)

Let's reduce it to something that even non-scientists can understand.

While health testing is admirable and a great beginning to a healthy future for dogs, no amount of health testing can substitute for outcrossing to produce robustly healthy dogs.

For the good of our breeds and all the dogs of the future, we need to change the current dog competition system. Conformation competition should be de-emphasized and standards need to be relaxed and more generalized. While today's dog shows do recognize and reward placid temperament, that is usually a secondary consideration to physical conformation characteristics.

If we want to improve the health of our breeds, the priority needs to be shifted to breeders who employ low levels of inbreeding; to those who breed first and foremost for excellence in temperament and ability as a worker or as a companion. Closed stud books need to be opened, and judicious crosses need to be allowed. Individual breed clubs need to invite outside genetics experts to help them develop policies to effectively manage their breed population.

The good work of AKC's Canine Health Foundation can and should be expanded. Beyond identifying genes that cause disease, the Foundation could employ geneticists for specific recommendations on how to better control genetic disease occurrence.

Our actions now will determine the ultimate fate of our dogs. Are you ready for the revolution?


1 comment:

  1. Almost forgot to post some references to prior available studies:

    1) B.N. Bonnett, A. Egenvall, P. Olson, . Hedhammar, Mortality in Swedish dogs: rates and causes of death in various breeds, The Veterinary Record, 12/7/1997, S. 40 – 44)
    “Mongrels were consistently in the low risk category” (S. 41)

    2) P.D. McGreevy & W.F. Nicholas, Some Practical Solutions to Welfare Problems in Pedigree Dog Breeding, Animal Welfare, 1999, Vol 8, 329-331
    “Hybrids have a far lower chance of exhibiting the disorders that are common with the parental breeds. Their genetic health will be substantially higher.” (P338)

    3) A. Egenvall, B.N. Bonnett, P. Olson, . Hedhammar,Gender, age, breed and distribution of morbidity and mortality in insured dogs in Sweden during 1995 and 1996, The Veterinary Record, 29/4/2000, p. 519-57
    “Mongrel dogs are less prone to many diseases than the average purebred dog.” (S. 524)

    4) R. Beythien, Tierarten- und Hunderassenverteilung, Erkrankungshufigkeit und prophylaktische Manahmen bei den hufigsten Hunderassen am Beispiel einer Tierarztpraxis in Bielefeld in den Jahren 1983-1985 und 1990-1992, 1998, Diss., Tierrztl. Hochschule Hannover
    "Mongrels require less veterinary treatment"

    5) A. R. Michell, Longevity of British breeds of dog and its relationship with sex, size, cardiovascular variables and disease, Vet. Rec., 27 Nov. 1999, S. 625-629
    “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” (S. 627 – thus only small and toy breeds, as to be expected)

    6) G.J. Patronek, D.J. Walters, L.T. Glickman, Comparative Longevity of Pet Dogs and Humans: Implications for Gerontology Research, J. Geront., BIOLOGICAL SCIENCES, 1997, Vol 52A,No.3, B171-B178
    “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.” (p. B173)

    7) H.F. Proschofsky et al, Mortality of purebred and mixed breed dogs in Denmark, Preventive Veterinary Medicine, 2003, 58, 53-74
    Higher average longevity of mixed breed dogs (grouped together). Age at death mixed breeds (Q1 Q2 Q3 mixed breeds 8,11,13, purebreds 6, 10, 12)