COI % and Inbreeding

The ideal COI for your dogs is anything under 15%. Above this level of inbreeding, an impact on the quality of the dog is felt heavily and increases exponentially as the inbreeding increases.  COIs under 15% have no negative impact on dogs.

Common Relationships

  • 25.00% - parent/offspring or full brother/sister cross
  • 12.50% - half brother/sister, grandparent/grandpup, or double first cousins crosses
  • 9.75% - great uncle or aunt/great niece or nephew cross
  • 6.25% - first cousins

Frequently Asked Questions

Where can I find the COI?

The COI of each dog is located on their dog info page, directly below generation number. The COI for a potential litter is located next to the sires name on the breed bitch page, and beside the bitches name on the use stud page.

How many generations back does inbreeding go?

Currently, it goes back four-generations but there is a chance that may be increased in the future.  Four generations back is the generation in which there are 16-ancestors.

Does the COI of my dog change as it gets older?

No. Your dog's COI will never change.

What is COI?

Technically, the COI is the probability that both genes of a pair in a dog are identical.  Simply put, it's a measurement of inbreeding. COI is calculated for you so it is not necessary to understand the mathematics behind it.

It is calculated by a mathematical formula that is somewhat complicated to many users.  The function is...

COI = sum[ (.5 ^ (a + b + 1)) * (1 + c) ]

a = Generations between sire and common ancestor
b = Generations between dam and common ancestor
c = COI of common ancestor

If a common ancestor does not show up on both the top and bottom sides of a pedigree, it will not impact the COI of the dog.  Using this principle, you may breed a highly inbred bitch to a highly inbred dog and end up with hybrid offspring that do not have any inbreeding whatsoever.

If you don't understand that formula, don't worry, it's not necessary to know how to calculate it.  The COI for all dogs will be in the dog info pages and displayed on hypothetical breedings before they are confirmed.

Why does my dog that is the result of a father/daughter breeding have a COI higher than 25%?

If a common ancestor is inbred, it will increase the COI of its resulting offspring if they are inbred to it. The more names appearing multiple times in a dogs pedigree the higher the COI.

Last Updated: 5/30/2011 8:11:44 PM

Did you know?
The third obedience title is a UD, or "Utility Dog", which is earned through competition in the Utility obedience class