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Coefficient of inbreeding-COI

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.


Inbreeding and linebreeding are NOT the same. inbreeding is breeding two very closely related dogs, mother-son, father-son, brother and sister. Linebreeding is breeding two dogs that share relatives several generations back, but DO NOT share the same mother, father or grandparents. Therefore, breeding a male dog and a female dog that share a great-great-great grandfather would be considered linebreeding. Reputable breeders DO NOT inbreed and it should NOT be done. Reputable breeders do however linebreed, this is done to preserve some of the aspects of the line, but it is not in-breeding and reputable breeders are very careful to closely study dogs' pedigrees to make the best possible match.


An Outcross is when two dogs that do not share any of the same ancestors within a certain number of four generations. The best way to gauge whether a cross is or is not an outcross is by calculating the COIs of the parents and the proposed litter. If the result for the cross is low (under 6.25%) or at least substantially lower than that of the lowest parental COI, it can be termed an outcross.



Common Relationships
25.00% - is equivalent to a parent/offspring or full brother/sister cross

12.50% - is equivalent to a half brother/sister, grandparent/grandpup, or double first cousins crosses

  9.75% - is equivalent to a great uncle or aunt/great niece or nephew cross

  6.25% - is equivalent to first cousins


It is highly recommended to avoid COI percentages in excess 15% and a COI in excess of 20% should be totally avoided.


What is COI?
COI is the calculation of the level of inbreeding in a dog or litter.


High COI percentages increase the probability that genetic defects will be carried from common ancestors on both sides

of the pedigree and will match up to cause the actual genetic disease or defect in the animal.

Many other problems of a high COI also affect dogs, such as Autoimmune disease and inbreeding depression symptoms,

which result in reproductive and longevity issues.


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. 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.


In Conclusion:

Pedigree Analysis Reports are valuable tools that can help give us a sense of which dogs in the pedigree will be the largest genetic contributors to a litter.  Once those individuals are identified, they can be researched further to get a sense of which genes they do carry.  However, it is not the only tool a breeder should rely upon.  These numbers alone do not give enough information about the dogs to be the sole basis for planning a litter.  Breeders must always take into account the actual dogs that are being considered for breeding.  In addition to their individual health, temperament and structure, breeders must also attempt to learn as much information as possible about their siblings and parents.


Coefficient of Inbreeding, or COI, as it is more commonly known, is just a way of determining the level of inbreeding for the chosen dog.  Which seems to be the latest buzz word on the Internet, amongst those interested in dog breeding, it should be remembered that it is only one of many useful tools to help the breeder produce a healthy litter, in the same way that Hip Scores and DNA test results are useful.  Obviously when breeding a litter, or planning a litter, all other aspects should be taken into consideration.  The COI should be seen in context with everything else and not used as the only deciding factor.  Bear in mind that it is perfectly possible for a dog with a high COI to not have, or to not produce health problems and equally it is perfectly possible for a dog with a low COI to have, or to produce health problems.  It is after all just another useful tool for the breeder.

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