Abstract
BackgroundCanine Hip Dysplasia (CHD) is a common inherited disease that affects dog wellbeing and causes a heavy financial and emotional burden to dog owners and breeders due to secondary hip osteoarthritis. The Orthopedic Foundation for Animals (OFA) initiated a program in the 1960's to radiograph hip and elbow joints and release the OFA scores to the public for breeding dogs against CHD. Over last four decades, more than one million radiographic scores have been released.Methodology/Principal FindingsThe pedigrees in the OFA database consisted of 258,851 Labrador retrievers, the major breed scored by the OFA (25% of total records). Of these, 154,352 dogs had an OFA hip score reported between 1970 and 2007. The rest of the dogs (104,499) were the ancestors of the 154,352 dogs to link the pedigree relationships. The OFA hip score is based on a 7-point scale with the best ranked as 1 (excellent) and the worst hip dysplasia as 7. A mixed linear model was used to estimate the effects of age, sex, and test year period and to predict the breeding value for each dog. Additive genetic and residual variances were estimated using the average information restricted maximum likelihood procedure. The analysis also provided an inbreeding coefficient for each dog. The hip scores averaged 1.93 (±SD = 0.59) and the heritability was 0.21. A steady genetic improvement has accrued over the four decades. The breeding values decreased (improved) linearly. By the end of 2005, the total genetic improvement was 0.1 units, which is equivalent to 17% of the total phenotypic standard deviation.Conclusion/SignificanceA steady genetic improvement has been achieved through the selection based on the raw phenotype released by the OFA. As the heritability of the hip score was on the low end (0.21) of reported ranges, we propose that selection based on breeding values will result in more rapid genetic improvement than breeding based on phenotypic selection alone.
Highlights
There are an estimated 60–70 million pet dogs in USA households
As the heritability of the hip score was on the low end (0.21) of reported ranges, we propose that selection based on breeding values will result in more rapid genetic improvement than breeding based on phenotypic selection alone
Our goal was to determine if improvement in hip phenotypes, as has been reported in the Orthopedic Foundation for Animals (OFA) database over the last four decades [11,12], has been accompanied by improvement in a breed’s genetic potential for nondysplastic hip conformation
Summary
There are an estimated 60–70 million pet dogs in USA households. The selective crossing, and line breeding, that generated pure dog breeds inadvertently caused fixation of recessive alleles that predispose to inherited disorders. Canine Hip Dysplasia (CHD) is a developmental disease that is expressed between 2 and 6 months of age for most medium and large dog breeds. It is a major veterinary medical problem with estimates of over 40% dysplastic dogs in some large breeds [1] and up to 75% as reported by the Orthopedic Foundation for Animals (OFA) (www.offa.org). Inherited developmental traits like hip and elbow dysplasia cause much of the osteoarthritis that plagues dogs as they age and could be prevented by better breeding practices. Canine Hip Dysplasia (CHD) is a common inherited disease that affects dog wellbeing and causes a heavy financial and emotional burden to dog owners and breeders due to secondary hip osteoarthritis. More than one million radiographic scores have been released
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