The COI Chronicles

by Ric Plath & Ellen Bergfeld, Castiron Kennels

This 3-Part Series was published in the April ’23 issue of the NAVHDA Versatile Hunting Dog magazine, and is used by the University of Kentucky Program in Animal Genetics. The series has been updated to include a clarification about how most pedigree software understates COI calculations by not including ‘Missing Dogs” in the calculation.

Coefficient of Inbreeding (COI) calculations were developed as a way for breeders to manage risk when breeding “purebred” dogs.  The COI is a mathematical statistic calculated for a breeder to evaluate the downside risk of a breeding.  

Breeding resulting in a “high” 10-Generation COI, defined as >10%, will likely result in a loss of hybrid vigor and could have an adverse effect on the overall health of a breed over time. HOWEVER, a high COI will more consistently produce offspring that look and act like their parents than a low COI.

Although the Coefficient of Inbreeding (COI) is important, there’s much more to successful breeding programs…those that continue to produce excellent dogs year-after-year…than COI.