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[NOTE: It’s easy to blame common dog health issues like allergies or joint pain on breeding, but it may actually be stemming from the immune system! Click here to download your free Leaky Gut Workbook and start healing your dog from the inside out.]

Whether you have a purebred dog or a “Heinz 57,” you’ll probably be interested in the answer to this question.

Many people suggest that purebred dogs are more prone to genetic disorders than mixed breed dogs.

The theory is that breeders selecting for specific traits can cause more frequent genetic disorders in purebred dogs. By contrast, the random mating of mixed-breed dogs can increase “hybrid vigor” – meaning greater health and resistance to disease.

But researchers at University of California-Davis (UC-Davis) weren’t so sure. Since all domestic dogs come from three to five wolf lineages, you might expect the common ancestry to create disorders common to all breeds.

So read on … the results may surprise you! And they might give you some insight into your dog’s potential to get certain diseases.

[NOTE: It’s easy to blame common dog health issues like allergies or joint pain on breeding, but it may actually be stemming from the immune system! Click here to download your free Leaky Gut Workbook and start healing your dog from the inside out.]

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Less Popular Breeds Come From Smaller Gene Pools

According to American Kennel Club (AKC) records, in 2004 there were more than 140 AKC registered breeds. The most popular ten of these breeds made up more than half of AKC registered dogs. The 100 least popular breeds accounted for less than 15% of all registrationss

Less popular breeds would have smaller gene pools.  Portuguese Water Dogs, which ranked 56th in registrations in 2011, go back to about 6 ancestors. These 6 ancestors form 80% of the current PWD gene pool. So a breed with a smaller gene pool (and thus less genetic variation) would be more likely to have a recessive disorder.

Before this study, most studies had focused on a single disorder and its tendency in a particular breed. But the UC-Davis researchers Bellumori TP, Famula TF et al wanted to find out about the prevalence of inherited disorders in the dog population as a whole.

The Disorders

From 1995 to 2010, the researchers studied 27,254 dogs with inherited disorders at University of California-Davis Veterinary Medical Teaching Hospital.

They studied 24 different disorders in five categories:

Cancers

  • Hemangiosarcoma
  • Lymphoma
  • Mast cell tumor
  • Osteosarcoma

Cardiac disorders

  • Aortic stenosis
  • Dilated cardiomyopathy
  • Hypertrophic cardiomyopathy
  • Mitral valve dysplasia
  • Patent ductus arteriosus
  • Ventricular septal defect

Endocrine disorders

  • Hyperadrenocorticism
  • Hypoadrenocorticism
  • Hypothyroidism

Orthopedic disorders

  • Elbow dysplasia
  • Hip dysplasia
  • Invertebral disk disease (IVDD)
  • Patellar luxation
  • Ruptured cranial cruciate ligament

Other

  • Atopy or allergic dermatitis
  • Bloat
  • Cataracts
  • Epilepsy
  • Lens luxation
  • Portosystemic shunt

Dogs In The Study

The study divided the dogs into two different designations:

  • Purebred dogs, including AKC-recognized breeds, AKC miscellaneous breeds and Foundation Stock Service breeds
  • Mixed breed dogs

The researchers excluded non-domesticated patients like dingoes or wolves. They also evaluated Pit Bull type dogs separately because it was hard to validate their purebred status.

Control dogs for each disorder came from healthy dogs evaluated at the teaching hospital during the 15-year period. The researchers classified healthy dogs by age, weight and sex (including whether neutered or not), then matched these dogs to each affected dog for the conditions. They then randomly selected the control dogs for each disorder.

The Results

The study showed that the theory of purebred dogs being more susceptible to disease doesn’t really hold up.

Dogs With Or Without Disorders

Of 90,004 dogs examined, 27,254 had more than one of the disorders and 62,750 were control dogs

  • 15 breeds had over 20% of dogs with more than one disorder
  • 63 breeds had from 21% to 30%
  • 41 breeds had from 31% to 40%
  • 10 breeds had more than 40%

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Disorders Similar For Purebred Vs Mixed Breed

Of 24 disorders the researchers monitored, 13 were about the same in purebred vs mixed breed dogs (matched for age, sex and body weight).

All the cancers

Hemangiosarcoma
Lymphoma
Mast cell tumor
Osteosarcoma

Cardiac

Hypertrophic cardiomyopathy
Mitral valve dysplasia
Patent ductus arteriosus
Ventricular septal defect

Orthopedic

Hip dysplasia
Patellar luxation

Endocrine

Hypoadrenocorticism
Hyperadrenocorticism

Other

Lens luxation

More Prevalent in Purebred Dogs

But ten disorders were more prevalent in purebred dogs than in mixed breed dogs.

Cardiac
Aortic stenosis
Dilated cardiomyopathy

Endocrine
Hypothyroidism

Orthopedic
Elbow dysplasia
IVDD

Other
Atopy or allergic dermatitis
Bloat
Cataracts
Total epilepsy
Portosystemic shunt

Genetic Dog Diseases: More Prevalent In Mixed Breeds

Only one disorder – cranial cruciate ligament rupture – was more likely in mixed-breed dogs than purebred dogs. The risk was significantly higher – 30%. The reason could be that combining different physical conformations reduces the resilience of the ligaments.

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Is Your Breed On The List?

Among the ten genetic disorders with a significantly greater probability in purebred dogs, the top breeds with each disorder are shown below. It’s interesting to note that some conditions are predominant among very small or very large breeds.

Aortic stenosis

Newfoundland (6.80%)
Boxer (4.49%)
Bull Terrier (4.10%)
Irish Terrier (3.13%)
Bouvier des Flandres (2.38%)
Mixed breed (0.15%)

Dilated cardiomyopathy

Doberman Pinscher (7.32%)
Great Dane (7.30%)
Neapolitan Mastiff (6.52%)
Irish Wolfhound (6.08%)
Saluki (5.88%)
Mixed breed (0.16%)

Elbow dysplasia

Bernese Mountain Dog (13.91%)
Newfoundland (10.28%)
Mastiff (6.55%)
Rottweiler (6.31%)
Anatolian Shepherd Dog (5.41%)
Mixed breed (0.90%)

IVDD

Dachshund (34.92%)
French Bulldog (27.06%)
Pekingese (20.59%)
Pembroke Welsh Corgi (15.11%)
Doberman Pinscher (12.70%)
Mixed breed (4.43%)

Hypothyroidism

Giant Schnauzer (11.45%)
Irish Setter (7.69%)
Keeshond (6.63%)
Bouvier des Flandres (6.55%)
Doberman Pinscher (6.30%)
Mixed breed (1.54%)

Atopy or allergic dermatitis

West Highland White Terrier (8.58%)
Coonhound (8.33%)
Wirehaired Fox Terrier (8.16%)
Cairn Terrier (6.91%)
Tibetan Terrier (5.86%)
Mixed breed (1.08%)

Bloat

Saint Bernard (3.76%)
Irish Setter (3.42%)
Bloodhound (3.39%)
Great Dane (2.80%)
Irish Wolfhound (2.70%)
Mixed breed (0.20%)

Cataracts

Silky Terrier (22.76%)
Miniature Poodle (21.49%)
Brussels Griffon (20.51%)
Boston Terrier (19.61%),
Tibetan Terrier (18.92%)
Mixed breed (4.04%)

Epilepsy

Catahoula Leopard Dog (3.90%)
Beagle (3.57%)
Schipperke (3.42%)
Papillon (3.40%)
Standard Poodle (3.19%)
Mixed breed (0.91%)

Portosystemic shunt

Yorkshire Terrier (10.86%)
Norwich Terrier (7.41%)
Pug (5.88%)
Maltese (5.87%)
Havanese (4.35%)
Mixed breed (0.35%)

Conclusion

  • The theory that purebred dogs are more susceptible to inherited diseases only holds true for some disorders (10 out of the 24 studied).
  • The prevalence of disorders among purebred and mixed-breed dogs varied with the condition. Some conditions (14) have a clear distinction between purebred and mixed-breed dogs and others (10) show no difference.
  • The results gave insight into the ability of breeding practices to reduce prevalence of disease. Reliable genetic tests or screening at a young age could reduce some disorders in the dog population as a whole.
  • The researchers also commented that some disorders may require breed registry intervention to reduce selection pressures that contribute to a certain disorder in a breed
  • “Recently derived breeds” or breeds from similar lineages were more susceptible to certain disorders that affect all closely related purebreds
  • Disorders with equal prevalence in purebreds or mixed breeds seemed to be more ancient mutations that are widely spread through the dog population

So, for many diseases, this study debunks the theory that purebred dogs are more susceptible. However, for the ten disorders where purebred dogs are at higher risk, and your breed is on the list, this information may help you take preventative steps to protect your dog from some disorders.

If you’re interested in more detail, here’s the whole study.

[NOTE: It’s easy to blame common dog health issues like allergies or joint pain on breeding, but it may actually be stemming from the immune system! Click here to download your free Leaky Gut Workbook and start healing your dog from the inside out.]

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