COI explained

[Raven]

How does COI work? A high COI is good or bad? How can I improve my horses genetic potential without triggering the COI?

[Nate]

COI is coefficient of inbreeding. It serves as an estimate of homozygousity in that particular horse's genes, but it is an estimate only based on the ancestors that occur more than once in the last 7 generations. As such, a horse can be 100% homozygous with 0% COI, and 100% heterozygous with a very high COIm those scenarios, however, are so exceedingly rare that they are essentially impossible.

Inbreeding, and therefore a high COI, is not in and of itself a good or bad thing. What matters is what horses you choose to inbreed. If you choose horses with low GP, then you will solidify the genes for low GP in your herd and in time, it will never produce anything else. If you inbreed horses with high GP, the same thing will result.

COI is really only useful as an estimate of how likely the horse is to pass on their genes as you see them. Whether or not high COI is a bad thing in your herd is entirely up to you. Breed well and it will be good. Breed poorly and it will be bad.