Reducing the Frequency of Hip Dysplasia: A Progress Update

Between January 1,1974 and January 1,1995 OFA evaluated radiographic submissions on 454,725 dogs from 221 breeds that were 24 months of age or older. The submissions were voluntary and were independently evaluated by 3 veterinary radiologists as being normal (excellent, good or fair), borderline or dysplastic (mild, moderate or severe). The evaluation procedure is carefully monitored for consistency over time. The radiographic evaluation procedure remained constant for this report period. The results of the procedure were also constant - all 3 of the radiologists agreed on the evaluation of normal, borderline, or dysplasia in approximately 94% of the cases and on the specific rating in approximately 80% of the cases for this report period. The findings are applicable to this specific population, a subset of the general population of dogs, and represent the majority of breeding or potential breeding dogs.

Screening of the radiographs by the attending veterinarian, prior to submissions, appears to affect the reported frequency of dysplasia in each breed. Therefore, OFA data under reports the frequency of dysplasia in the general population for each breed. However, use of the OFA data to document breed progress is valid, as all breeds were similarly affected and the effect of prior screening appears to have been constant over this reporting period. Note that similar breeds had different levels of progress and 4 breeds demonstrated an increase in dysplasia.

Changes in frequency of dysplasia appear to be the direct result of selective breeding practices used by the breeders. The number of breeders that choose to breed only dogs found to be normal has increased, but a few breeders still choose to breed dysplastic dogs for a myriad of reasons. Only the breeder chooses which dog is to be bred with which bitch; therefore, the breeder controls the occurrence of dysplasia in his/her breed.

Grouping data for all breeds revealed the following:

1. Females tended to have a higher frequency of dysplasia than males. This was significant in some breeds but not in others.
2. All breeds with 45 or more submission demonstrated some frequency of dysplasia.
3. There was a significant (P less than .05) decrease in dysplasia from 17.4% in dogs born before 1981 (n=127, 297) when compared to 12.4% in dogs born in 1991 and 1992 (n=50, 428). The decline was evident in the mild and moderate categories with the severe category remaining essentially the same. There was a corresponding increase in the excellent and good categories indicating improvement of hip quality in most breeds.
4. Breeders and breed clubs in many breeds did not start emphasizing control of dysplasia until the mid 1980's.
5. Use of information on family hip status by breeders was slower in some breeds than others. Mass selection (breeding normal to normal) appeared to be the most commonly used breeding practice.

Progress, or lack of same, was calculated for 71 breeds with 500 or more submissions by comparing the frequency of dysplasia in dogs born in 1980 and before with the frequency in those born in 1991 and 1992. In most breeds, OFA evaluated a significant percent of the breeding population. The results from 2 breeds where over 90% of the breeding population was evaluated are as follows:

PORTUGESE WATER DOG
BORN      NUMBER  %EXCELLENT    %DYSPLASTIC
   1980     102       1.0       26.5
  81-82      76       7.9       19.8
  83-84     116       4.3       25.8
  85-86     227       4.8       21.2
  87-88     280      10.4       18.9
  89-90     394       9.9       13.0
  91-92     345      10.4        8.4

BERNESE MOUNTAIN DOG
BORN      NUMBER  %EXCELLENT    %DYSPLASTIC
   1980     566       2.8       32.8
  81-82     305       2.0       26.0
  83-84     363       5.2       26.2
  85-86     532       5.6       22.4
  87-88     694       7.3       22.5
  89-90     720       7.1       16.4
  91-92     740       9.1       12.6

In these breeds, like all others, we know that some breeders chose to breed dysplastic dogs, but this number is decreasing as the availability of more normal dogs with the desirable breed characteristics increases. The frequency of dysplasia in the Portuguese Water Dog was reduced by 68.3% and in the Bernese Mountain Dog by 61.6%. The frequency of excellents dramatically increased in both breeds.

It is clear that with the exception of 5 breeds (Boykin Spaniel, Flat Coated Retriever, Afghan Hound, Kerry Blue Terrier, and Komondor) breeders have made great progress in reducing the frequency of dysplasia. The results of 71 breeds with 500 or more submissions are as follows:

REDUCED THE FREQUENCY OF DYSPLASIA BY MORE THAN 70%
  Borzoi                          Soft Coated Wheaten Terrier
  Rhodesian Ridgeback             Welsh Springer Spaniel
  Siberian Husky                  Wirehaired Pointing Griffon

REDUCED THE FREQUENCY OF DYSPLASIA BY 60-70%
  Bearded Collie                  Portuguese Water Dog
  Bernese Mountain Dog            Puli
  Doberman Pinscher

REDUCED THE FREQUENCY OF DYSPLASIA BY 50-60%
  Australian Shepherd             English Setter
  Bichon Frise                    German Wirehaired Pointer
  Brittany                        Old English Sheepdog
  Collie                          Shar Pei
  English Cocker Spaniel          Shetland Sheepdog

REDUCED THE FREQUENCY OF DYSPLASIA BY 40-50%
  Akita                           Giant Schnauzer
  Bloodhound                      Kuvasz
  Border Collie                   Norwegian Elkhound
  Boxer                           Samoyed
  Cocker Spaniel                  Tibetan Terrier
  Dalmatian                       Vizsla
  English Springer Spaniel        Weimaraner
  German Shorthaired Pointer                I

REDUCED THE FREQUENCY OF DYSPLASIA BY 30-40%
  Airedale Terrier                Gordon Setter
  Belgian Malinois                Irish Setter
  Belgian Tervuren                Irish Wolfhound
  Briard                          Keeshond
  Bullmastiff                     Lhasa Apso
  Golden Retriever                Poodle

REDUCED THE FREQUENCY OF DYSPLASIA BY 20-30%
  Alaskan Malamute                Labrador Retriever
  Belgian Sheepdog                Mastiff 
  Bouvier Des Flandres            Newfoundland
  Cavalier King Charles Spaniel   Rottweiler
  Chesapeake Bay Retriever        Saint Bernard
  Chow Chow                       Standard Schnauzer
  Great Dane                      Staffordshire Terrier
  Great Pyrenees                  Welsh Corgi Pembroke

REDUCED THE FREQUENCY OF DYSPLASIA BY 10-20%
  Australian Cattle Dog           German Shepherd Dog

NO CHANGE IN FREQUENCY OF DYSPLASIA
  Boykin Spaniel

INCREASED THE FREQUENCY OF DYSPLASIA
  Afghan Hound                    Kerry Blue Terrier
  Flat Coated Retriever           Komondor