More Information About EBVs

EBVs communicate the genetic risk of hip/elbow score for individual dogs in reference to the entire breed. They can be compared to determine which breeding animals have a higher or lower genetic risk, a risk which will be inherited by their offspring/progeny.

EBVs are computed using available hip and/or elbow scores for the dog and all its relatives. Pedigree information is used to determine the relationships among all dogs therein. This allows the genetic risk of individuals to be evaluated, stripping away any environmental effects on the scores, which is important since only genes are inherited over generations. Using EBVs to make mating decisions will be more accurate than using the observed hip or elbow score and will lead to faster progress in reducing the prevalence of disease.

What do the values/figures mean?

  • The breed average is always set to 0. Higher risk EBVs are shown as a number higher than zero (positive number - red area on the left of the centre bar) and lower risk EBVs as a number lower than zero (negative number - green area on the right of the centre bar).
  • The further a dog's EBV is from the average, the higher or lower its genetic risk. One standard deviation is represented by 20 units. So a dog with an EBV of +40 has a genetic risk two standard deviations higher than the breed average, while a dog with an EBV of -20 has a genetic risk one standard deviation lower than the breed average.
  • The confidence is an indication of how much scoring/test information has been used to calculate the EBV. If the dog has been hip or elbow scored itself and has several relatives with scores then the confidence will be higher than if it has not been scored and has few relatives with scores. Individuals with several scored offspring tend to have high accuracies. Confidence is the correlation between the estimate of the breeding value and the true value. The more information available the closer the estimate will be to the true value.
  • At birth a puppy's EBV will be the average of its parents' EBVs. A dog's EBV can change during its lifetime, either upward or downward, as more information becomes available, either about the dog itself or its relatives. The confidence of the EBV will increase to reflect the greater confidence in the estimate from additional information.
  • EBVs rely on good quality data - it is crucial that people continue to hip and elbow score their dogs. If not enough dogs are scored, the confidence decreases and it could mean that EBVs are not calculated by the Kennel Club.

How Can EBVs Help Breeders?

  • EBVs can give breeders more flexibility in choosing breeding stock, as they are a more accurate indicator of genetic risk than a single assessment of an individual dog's hip/elbow score. Previously, the best advice was to use dogs below the breed average - meaning that many dogs could have been excluded from a breeding plan if their scores were a significant consideration. However, it could be perfectly reasonable to use a dog with an individual score a bit over the breed average, as long as the EBV indicates low genetic risk with good confidence.
  • The lower the EBV the better - but you don't need to search out the dogs with the very lowest risk EBV. Selecting any animal with a lower risk EBV than average will still lower the risk of hip/elbow dysplasia, and this should be balanced with other important factors such as temperament, health test results, etc.

Why is Scoring Still Important?

  • EBVs are simply a more effective way of using the hip/elbow score information for breeding purposes - but they are NOT a replacement.  Their calculation relies on a large quantity of good quality score data. EBVs are regularly recalculated to make use of new score data and to provide them for newly registered dogs, so it is essential that scoring continues.  The best way to ensure good EBVs is to get your dogs scored, and use EBVs to indicate genetic risk in your breeding decisions.
  • Scoring individual dogs has tremendous value in indicating the actual degree of dysplasia present (or not) in an individual dog. The EBV estimates genetic risk - which is helpful for breeding - but does not take account of non-genetic factors which influence the severity of dysplasia. Hip/elbow scores remain the best diagnostic measure of hip and elbow dysplasia, and will allow/help owners to adjust known non-genetic influences (such as exercise intensity or duration) to minimise the effects of these diseases where they occur.
  • EBVs change over time, as more dogs are scored. So, by continuing to score, you improve the confidence of the EBV, and therefore the quality of information you use to make breeding choices.

Acknowledgements

Estimated Breeding Values on the Kennel Club's Mate Select platform were created as a collaboration between the Kennel Club and the Kennel Club Genetics Centre, at the Animal Health Trust. The Kennel Club gratefully acknowledges the technical input and advice of Professor John Woolliams (The Roslin Institute, University of Edinburgh) in the development of the models for calculation and presentation of EBVs. The Kennel Club gratefully acknowledges Professor Brian Kinghorn (The University of New England, Armidale, Australia) for advice on the visual presentation of EBVs.

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