The OFA score (a measure of the dog’s hip conformation) collected over the past 40 years has provided a selection criteria for dog breeders and buyers. However, the data that is available in the public part of the OFA data base has been difficult to access by the dog owning and breeding members of the public. Our analysis of the Labrador Retriever OFA hip breeding values over that period showed that there has been slow but consistent genetic improvement. A PDF of this page is attached. Here we summarize some salient points about breeding values and their application to improvement of OFA style hip scores. The explanation and methods that form the basis of the breeding values available in the search page of this web site were published in the American Journal of Veterinary Research in 2008 by Zhang et al. and a PDF of that paper is available in the publication section. The methods we have used here in calculation of breeding values and inbreeding coefficients are an extension of that work but here applied only to hip scores in the public OFA data base.
The breeding value in its earliest use was also called the selection index. The selection index was based on integration of genetic (pedigree relationships) and phenotypic information (OFA hip scores in our case) from each animal and its relatives and yielded better results than phenotypic selection alone for desired traits. The accuracy of the selection index of a subject increases when the OFA scores from its close relatives (e.g. progeny and ancestors) are included in the estimation. The selection index was developed into the Best Linear Unbiased Prediction (BLUP). The BLUP breeding strategy has been used successfully for genetic improvement, particularly in livestock, and has also been applied in closed colonies of dogs with substantial success. Implementation of the BLUP strategy was enhanced by methods of variance component estimation, such as restricted maximum likelihood. Variance components attributable to additive genetic and residual effects were estimated for the hip score breeding values and inbreeding coefficients accessible in this web site. The hip score breeding values in the search page range from the Labrador Retriever with the best hip conformation of -0.95 (lower breeding value means a better hip) and the dog with the worst hip score breeding value of 1.15. Our previous report by Zhang et al., (2008) demonstrated that a hip selection index that included an additional hip measurement like the distraction index or dorsolateral subluxation score along with the OFA type score and a Norberg angle measured from the OFA radiograph could be more effective in reducing the incidence of hip dysplasia than use of a single phenotypic measurement. However, the breeding values presented here rely solely on the public OFA hip scores. Generally, most breeders and dog purchasers will only have access to either an OFA score or a distraction index when they collaborate with a veterinarian who is a member of the PennHIP™. Our unpublished data in the paper under review shows that the OFA scores correlated well with the OFA hip score breeding value when plotted against birth years.