[YardleyLabs]

I think it's a fair observation that has no simple answer. Hip dysplasia is much more complicated than EIC. A high percentage of dogs classified as dysplastic will never show significant symptoms. The inheritance is polygenic -- that is, many genes are involved -- and the rate of inheritance is both lower and more variable than the rate of inheritance for a simple autosomal recessive like EIC.

The observed incidence of HD among OFA tested dogs is approximately equal to what would have been expected from random breedings of OFA good to good dogs (11-12%) suggesting that there have been some benefits from selective breedings. I suspect, but have no way of knowing, that the incidence among dogs that are not being screened is twice that level.

I also suspect that the incidence among OFA tested dogs would be lower except for the willingness to breed OFA Fair dogs to OFA Good dogs based on performance achievements of the dogs with Fair hips. This combination has a much higher incidence of dysplasia among offspring than either a Good x Good breeding or an Excellent x Fair breeding or than is observed in the general population of tested dogs. It seems to me that iof you are going to breed a dog with Fair hips that it is worth looking for a mate with excellent hips rather than anythig lower.

The PennHIP recommendation of breeding only dogs rated in the 50th percentile or better would effectively exclude almost all dogs rated Fair and a significant percentage of those rated good. Following that recommendation would probably have a beneficial impact on the incidence of dysplasia but only by excluding some extraordinary dogs.

The more interesting and challenging issue may be seen if a specific conformation test is developed that helps predicts the incidence of ligament injuries with some degree of precision.

On balance, I think breeding decisions need to balance the variety of health, temperament, and performance issues rather than focusing only on one or two factors. However, I do believe that breeders have a responsibility for informing purchasers of what they know of both the positives and negatives of dogs they choose to breed so that purchasers can make their own decisions with as much information as possible.

 

[YardleyLabs]

Thanks Jeff, the problem or possible problem is with the missing information from the OFA database, that being the potentially statistically significant number of dysplastic dogs that are not sent to OFA and therefore not in the statistical evaluation of the available data. Do we know where the statistics for potential for dysplasic occurance from the different matings comes from? Is it missing this vital piece of data as well?

I think it's fair to assume the data are missing. When I am evaluating OFA data, I tend to focus more on the ratio of excellents to fairs in the vertical and horizontal lineage of the litter parents, grand parents, and great grand parents. I prefer PennHIP for my own dogs, but there is not enough data available for it to provide me with information for planning breedings..