Inbreeding Coefficients
At Bruiser Bulldogs, we believe that preserving the future of the English Bulldog means rethinking how we approach breeding—starting with genetics. One of the most important tools we use in our program is the inbreeding coefficient (COI), which helps us measure how genetically related a potential pair is. The following is a chart to help understand COI.
| COI (%) | Interpretation |
| 0–5% | Excellent — high genetic diversity |
| 6–10% | Acceptable for most breeds |
| 10–20% | Caution — monitor health closely |
| >20% | High inbreeding — avoid if possible |
Keeping COI’s low allows us to maintain genetic diversity in our bloodlines as well as reduce the probability of undesirable recessive genetics popping up in our bloodlines. This approach is in starch contrast to historical dog breeding which has used closely related dogs to create uniformity and conformation. While effective in creating unformed dog breeds, many breeds including the English Bulldog are now suffering from a lack of genetic diversity in their gene pool. Rather than rely on tradition – we focus on the science of genetics. A landmark study from UC Davis revealed that the modern English Bulldog suffers from dangerously low genetic diversity, the result of generations of closed registries and breeding for exaggerated features. The time for tight breed conformity has ended, as genetic diversity and health should dictate our breeding decisions.
