If you are choosing a stud dog on the strength of his own hip score, you are working with one of the least reliable numbers available to you. For polygenic conditions like hip and elbow dysplasia, an individual’s phenotype — the score the vet or radiologist assigns to that one dog — reflects both its genes and a lifetime of environmental noise: growth rate, body weight, exercise, even how the dog was positioned for the X-ray. Estimated Breeding Values (EBVs) were developed to cut through that noise and answer the only question that matters for a breeder: what is this dog likely to transmit?
Why a Single Hip Score Misleads You
Hip dysplasia is not controlled by one gene. It is the combined effect of many genes of small effect, layered on top of strong environmental influences. That is the textbook definition of a polygenic trait, and it has a hard consequence: two dogs with identical, excellent hip scores can carry very different genetic loads. One may have good hips because of good genes; the other may have good hips despite mediocre genes, helped by lean body condition and careful rearing.
When that second dog is bred, the environmental luck does not pass to the puppies — only the genes do. This is why kennels can do everything “right,” breeding score-to-score for generations, and still see dysplasia resurface. Selecting on phenotype alone captures perhaps half of what you actually care about. For more on the underlying biology, see our overview of hip dysplasia genetics in herding breeds.
What an EBV Actually Is
An EBV is a statistical estimate of the genetic merit a dog will pass to its offspring, expressed as a deviation from the breed average. It is calculated using a model (the “animal model,” borrowed from livestock genetics) that pools phenotype data not just from the dog itself, but from its parents, siblings, half-siblings, offspring, and wider relatives — sometimes thousands of related animals.
The logic is simple. If a dog has a fair hip score but every sibling and both parents scored excellent, the family data tells you its genes are probably better than its own X-ray suggests. Conversely, a dog with a good score whose relatives are riddled with dysplasia is a riskier bet than its individual number implies. EBVs formalise that intuition mathematically.
The payoff is accuracy. Studies of British Veterinary Association / Kennel Club hip data have shown EBVs to be roughly 1.16 to 1.34 times more accurate than the dog’s own score at predicting offspring outcomes. That margin compounds over generations and is the single biggest reason schemes like the Estimated Breeding Values published for hip and elbow scores exist.
How to Read an EBV — and Its Confidence Rating
An EBV comes as two numbers, and you must read both.
The value itself is expressed relative to the breed mean, which is set to zero. For hip scores, where lower is better, a negative EBV is desirable — it means “below-average risk of transmitting dysplasia.” A dog at -8 is a better genetic bet than a dog at +5, even if their raw individual scores look similar. Always check which direction is “good” for the trait and scale you are reading; it is not always intuitive.
The accuracy (or confidence) rating, usually a percentage, tells you how much data sits behind the estimate. A young dog with no scored offspring and few scored relatives might have an EBV with 30–40% accuracy — useful, but provisional. An older, widely used sire with dozens of scored progeny can reach 80–90% accuracy, and his EBV will barely move with new data.
The practical rule: prefer a moderate EBV with high accuracy over a spectacular EBV with low accuracy. A flashy figure built on three relatives can swing wildly once real offspring data arrives. Treat low-accuracy values as a starting hypothesis, not a verdict, and re-check them as the dog matures and its EBV firms up.
Where EBVs Fit Alongside DNA Tests
It is tempting to assume DNA testing has made EBVs obsolete. It has not — the two tools cover different problems.
DNA tests are decisive for simple, single-gene (Mendelian) conditions: degenerative myelopathy, collie eye anomaly, MDR1 sensitivity. There, one or two markers explain the disease, the test gives a clear clear/carrier/affected result, and you can plan matings to avoid producing affected dogs. If you are newer to that side of things, our guide to canine DNA testing walks through how to interpret those results.
But for hip dysplasia, elbow dysplasia, and most behavioural and conformational traits, no single marker explains the trait. The genetic signal is spread across hundreds of variants, and commercial panels simply cannot give you a reliable “risk” call for an individual dog yet. This is exactly the gap EBVs fill. Until polygenic risk scores mature for dogs, EBVs remain the best population-level tool for selecting against complex disease.
The sophisticated approach is to use both: DNA tests to manage Mendelian disorders gene by gene, and EBVs to steadily push polygenic risk downward across your breeding program.
Putting EBVs to Work
A few practical habits turn the theory into better litters:
- Score and report everything. EBVs are only as good as the data feeding them. Every dog you have radiographed and scored — including the disappointments — improves the accuracy of your line’s estimates and the breed’s. Withholding poor scores corrupts the dataset everyone relies on.
- Select on the EBV, not the X-ray. When choosing between two mates, weigh the EBV and its accuracy ahead of the individual score. The score is one data point already baked into the EBV.
- Watch the breed trend. A good scheme publishes the breed’s average EBV over time. If it is drifting in the favourable direction, collective selection is working; if it is flat, the population is not improving regardless of individual choices.
- Combine traits sensibly. Do not chase the best hip EBV at the expense of elbows, temperament, or genetic diversity. Single-trait obsession narrows the gene pool and trades one problem for another.
EBVs will not give you a perfect puppy, and they cannot promise an individual dog’s joints will be sound. What they do is shift the odds in your favour, generation after generation — which, for a polygenic disease that resists every simpler fix, is precisely the win worth having.