What - no EBVs?
I was so disappointed that Steve Dean in his column last week on the 'Benefits of Canine Health Schemes' (CHS) did not mention Estimated Breeding Value (EBV) once, not once, yet EBV must be the biggest benefit to be developed from CHS.
Because scoring schemes for Hip Dysplasia (HD) and Elbow Dysplasia (ED) only describe the phenotype i.e. what the hips and elbows look like, and although they are better than no scheme at all, and using them will achieve improvement albeit slowly, they do not come anywhere near EBVs as a tool for improvement because EBV is an estimate of the genetic status of the dog for hips and elbows.
Steve said that "breeders will breed from those dogs having a low risk score", but what he should have said is that they should be breeding from low risk EBVs.
All is not clear cut when it comes to polygenic conditions. I know of many dogs that have what would appear to be low risk based on hip scores, but they have a substantially worse than average genetic risk. Such a dog is clearly the odd one out among all his relatives (ancestors and progeny), which have obvious HD problems in the breeding line, and using him for breeding, although he has a low HD score, will make hips worse. And the contrary also applies, as I know of dogs with, for example, poor ED scores yet they have good EBVs, indicating that they are the odd ones out in lines with good elbows.
The Kennel Club's own description of EBV says "Using EBVs to make mating decisions will be more accurate than using hip or elbow score and will lead to faster progress in reducing the prevalence of disease".
The KC's own brilliant geneticist Tom Lewis has stated in a published scientific paper "The use of EBV by dog breeders is projected to facilitate considerable improvement in hip and elbow joints in a wide range of breeds.
To achieve an improvement of 5 points in the median hip score via phenotypic selection would take from 30 to 300 years [depending on breed], but the same improvement [via genetic selection] using dogs with EBVs below the breed average would take between 9 years and 18 years [for the same two breeds]".
There are now 29 breeds with published EBVs for either hips or elbows or both. For these breeds EBVs are available for all registered dogs of the breed whether they have phenotypic scores or not (provided they have a scored relative no matter how distantly related). This is the great benefit to come out of CHS for hips and elbows.
For Steve Dean to say that "genetic tests designed to compete with health schemes for hips and elbows for example, will be some time emerging and may well prove disappointing" is frustratingly incorrect, although I fear that he is referring to DNA tests.
Tests that give the best estimate of genetic status are not futuristic, they are available now, they do not compete with health schemes, indeed they need health schemes for the calculation of EBV, and if used properly be breeders they will produce dramatic improvements, as they have been doing in the livestock sector for many decades. Dog breeders (and columnists) needs to move with the science.
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