Great question! This gets at a very important aspect of the genetics of health: breeding for improved health requires genetic diversity from which to selectively breed, but genetic diversity alone, in an individual dog, doesn’t determine health.
Our current measurement of genetic diversity isn’t a perfect proxy for “inbreeding”. Right now, it measures the differences between the maternal and paternal DNA, from which the dog has inherited one copy from each parent.
We are currently developing a better measurement, like COI. Here is a discussion about COI, and it brings up some points about COI being too low or too high:
I also want to emphasize that geneticists and dog professionals may use the word “inbreeding” differently. Here, it’s a number that describes genetic variation and all individuals have some level of it. For dog professionals, inbreeding refers to specific mating or family tree structures. Of course, the breeding leads to changes in the number, but the relationship isn’t 1-to-1.
Thank you for the question,