EBV

Will my dog's EBV ever change?

Yes. Although the genes are fixed at conception and do not change during the lifetime of an individual, the EBV…

Yes. Although the genes are fixed at conception and do not change during the lifetime of an individual, the EBV is an estimate of genetic risk, and this estimate will change as more information becomes available. For example, at birth a puppy's EBV is based on hip scores of its parents and other relatives. However, as the puppy grows it may be hip scored itself, as may some of its siblings. This extra information will be used in the regular calculation of EBVs. Eventually that dog may be used for breeding, and some of its progeny may be hip scored too. This information will also be used. All this extra information will increase the confidence of the estimate and may result in changes in EBV. So, a dog with an EBV of -8 and confidence of 80% may be a surer bet than a dog with an EBV of -10 but a confidence of only 30%.

EBVs will also change in another way too. Recall that the breed average is set to zero every time EBVs are calculated. However, the average of the breed will change as the breed responds to selection for lower hip scores over the generations. Thus, a young sire with an EBV of -10 in 2012, may by the end of his stud career only have an EBV of, say, -4. His own genetic liability will not have changed, but that of the wider breed will have done so in response to selection.

What does the confidence mean?

An individual's genetics are determined prior to birth and the EBVs are an estimate of the genetic risk. The confidence…

An individual's genetics are determined prior to birth and the EBVs are an estimate of the genetic risk.  The confidence reflects the estimate's proximity to the true value, and ranges from 0 to 100%. Higher accuracies mean we have more confidence in the estimates of genetic risk, because we have more information on that dog and its relatives. By way of comparison, without EBVs a dog's own hip score is an estimate of its true genetic risk of disease with a confidence of about 60%. This is because hip dysplasia (and therefore score) is influenced not only by genetics, but also by non-genetic and environmental factors, such as feed intake and exercise regime. The effects of these non-genetic influences may mask the true genetic risk of the disease.  For a dog without its own score but with scores of both parents known (the situation prior to dogs being scored at a minimum of 1 year old), the genetic risk is estimated with a confidence of about 40%.  The estimate of true genetic risk of a dog based on the score of a single parent only has a confidence of about 30%. Low accuracies indicate a lack of score information on a dog or its relatives and as a result we have little confidence that the EBV reflects the true genetic risk. The best way to remedy this is to get dogs hip/elbow scored. 

Does this mean an end to hip scoring our dogs?

No! EBVs are simply a more effective way of using the information we already have. It is important to remember…

No! EBVs are simply a more effective way of using the information we already have. It is important to remember that the estimates are only as good as the data used in their calculation. No more hip scores would mean no more EBVs.  Thus, the availability of EBVs does not mean an end to participating in hip scoring schemes, but does mean that greater progress can be made in genetic selection for low hip scores through the more effective use of score information. Furthermore, stopping scoring is not a way to improve a dog's EBV; the confidence will simply diminish. The best way to ensure good EBVs is to continue to score and use EBVs as the indicator of genetic risk in your breeding decisions. Finally but importantly, a dog's individual hip score still has tremendous value in indicating the degree of dysplasia in that particular dog. The EBVs estimate genetic risk, which is more useful in breeding strategy, but to determine the management of non-genetic factors known to influence the severity of dysplasia the hip score remains the best diagnostic measure. 

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