The COI: Co-efficient Of Inbreeding

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There's that scary word again - Inbreeding! According to the popular press, every time a purebred dog goes bad, it's because of "Inbreeding". Images of "dueling banjos" jump into our heads. But the results of selective inbreeding are all around us. That beautiful prize-winning rose? That Thanksgiving turkey you enjoy so much? Winter wheat? All the result of inbreeding. 

Every breed of dog is the result of inbreeding. Corgi's look like Corgi's and not like Great Danes because the founders of that breed inbred on dogs with short legs and other breed-specific features. The St Bernard is no exception. Certain dogs with certain features were used to set the genetic blueprint for what a St Bernard is to be. The written Standard then formalized that blueprint.

So if the very concept of inbreeding spooks you out, you probably shouldn't be in the dog breeding game.

I would like to talk here about a useful tool that every breeder should be using in their breeding program. It's called the Co-efficient Of Inbreeding or "COI".

The Co-efficient Of Inbreeding or COI is a mathematical tool for measuring the level of inbreeding in any animal based solely on its pedigree. It does NOT tell you anything whatsoever about the quality of those genes. More about that shortly.

If the COI is zero it means that none of the dogs on the father's side of the pedigree are the same as any of the dogs on the mother's side of the pedigree. The dog is a complete outcross.

On the other hand, if the COI is very high, say 25, the dog is highly inbred. If you breed a son back to his mother, or a daughter back to her sire, or full brother to a sister, that alone will result in a COI of 25. A half-brother to a half-sister would result in a COI of 12.5.

Our Yondo came from such a breeding. We bred Whisper to her half-brother, Energizer. Chesma was the mother of both of them. So, in effect, Yondo has only one grandmother, Chesma.


    AM CH Cronus vd Seekbacher-Ho HOF

CAN CH Scottandra's Rocket 

CAN CH Valais Astra v Scottandra 
CAN CH Benbaron's Energizer v Rocket 
CAN CH Scottandra's The Sting
Dancastle's Chesma 
CAN CH Benbaron's Lady Amanda Sisarah
AM/CAN CH Benbaron's Yondo v Gizer HOF PE
AM CH Echo's Just Me v Yondo
Echo's Unique von Just Me
AM CH Echo's Heather von Yondo
CAN CH Benbaron's Whisper v Unique
CAN CH Scottandra's the Sting
Dancastle's Chesma
CAN CH Benbaron's Lady Amanda Sisarah

Why would we do such a thing? We thought Chesma was an exceptionally powerful bitch with great mass, soundness and size. We wanted more of that in our program so we "doubled up" on her by breeding her offspring together. It worked! When you think of it, breeding comes down to getting as many "good" genes together as possible while eliminating as many "bad" genes as possible. Easy to say but devilishly difficult to do. Inbreeding works both ways. If you double up on good genes, you get better dogs. If you double up on bad genes, you get horrible dogs. That's the risk you take (and you must take calculated risks if you want to get anywhere in the dog game).

The value of the COI can change somewhat depending on how many generations of the pedigree you include in the calculation. A three-generation pedigree of Yondo yields a COI of 12.5 but a 5-generation pedigree produces a COI of around 14. That simply means that there are some related dogs further back in the pedigree but it also illustrates that the further back those dogs are, the less those dogs contribute genetically. To put it bluntly, just because Champion Great and Famous is your dog's great-great-great grandfather on both his father's and mother's side, it means bugger all genetically. His contribution to your dog is hardly noticeable.

The COI by itself is just a number. You have to know what it represents in your program. The trouble with genes is that we can't see them all with the naked eye. Some things are hidden or recessive. Why is it that some stud dogs pass on a certain, distinctive look or feature to their offspring on a consistent basis and others never seem to be able to reproduce themselves? Time and again, we have seen a dog pop up out of the blue and set new show records. People rush to breed to him but none of his puppies look like him. In most cases, such dogs are just genetic "sports" with a low COI. They have no concentrated genes to pass on.

In the St Bernard breed it is rare to see dogs with a COI above 6.5 (the number you get when you breed cousins or aunts and uncles). Far too many dogs being used in breeding have COI's of less than 2. To our way of thinking this just results in a bunch of "chop suey" pedigrees. Nothing is related. The puppies are just packages of random genes thrown together in the hope that something great will pop out. It rarely does and even if it does, such dogs almost never reproduce themselves. This is not the basis for creating a line of quality dogs that have a consistent look within litters, generation after generation.

Yondo died in 1988. At the 2011 National, a fancier friend of ours joked that "The Beningers have just been breeding the same dog over and over again!". He was referring at the time to Taboo and Xulu, both Yondo kids from frozen semen. We took his comment as the highest form of praise. Yondo has a relatively high COI of 14. We believe that helps explain why he now has 25 AKC champions to his credit with more on the way. We set out to concentrate good genes and he passed them on to his off-spring. Not all of his kids looked like him, of course, but you can sure see the "Yondo" in a lot of them.

We urge breeders to take the time to understand how to calculate the COI and use it to study their own pedigrees. Use it in advance of doing your next breedings. It's only a tool but no breeder should be without it. It should help you develop a plan to get to where you want to go in your breeding program. Good luck!