The Importance of COI in breeding

As with any breeding program one needs to consider traits such as style, intensity, natural ability, trainability, drive and conformation. However; we should also look at the Co-efficient of Inbreeding of our dogs. Below is a general explanation as to what COI% is and why we believe it needs to be used in helping us decide who we chose for breeding. Co-efficient of Inbreeding, or COI%, should not be the only factor we look at for a possible mating pair but it should be used in conjunction with other assessments to help us make informed decisions of who we choose to breed.

COI stands for Coefficient of Inbreeding. Basically it measures the common ancestors of the sire and the dam and helps indicates the probability of how genetically similar they are to each other. There are consequences to being too genetically similar, some good, some not so good. We often hear breeders talk about their litters being “Peas in a Pod” thus meaning the litter has a uniformity to it. This is often the result of breeding a higher COI%.

Every dog has some 20,000 genes that go into creating the dog and these are considered fixed genes. Each pup inherits from their sire and dam two identical copies of a particular gene. There are other genes that are passed on to the pup that are not as certain: coat color, temperament, build, gate, etc.

Many bloodlines have quite a few ancestors that are the same, when this happens there is little diversity and will also mean that the pup or parents will have a high COI%. The COI % is used to measure the probability of any pup or dog having the same identical gene passed down due to common ancestors.

Some dogs pedigrees already have high COI %, meaning the dog contains many single gene type. If both parents have a high COI% then this means that many of the genes that are passed on to the next generation will be the same in all the puppies, regardless of which parents are used. In other words, there is no breed diversity and thus the COI % will be high. The COI% measures the probability of any individual gene being common due to an identical gene being passed down to a puppy from both the sire and dam lines having some of the same common ancestors. Thus the pup will lack genetic diversity.

Measuring the COI in a dog is more than looking at just the parents. One needs to go back at least 10 to 11 generations to really have a true picture of what the true COI% is. With people we typically look back ten generations in our own family tree and it would be highly unlikely to see a particular name twice. However, with dogs this has not been the case. In some cases some dog’s names appear numerous times just in the first 8 generations. Breeders have done this in the past to make sure that certain traits are carried forward into the offspring of particular dogs that they like. The more a breeder does this the less diversity there is in a bloodline thus resulting in a high COI%.

There are two reasons that a high COI% is considered a problem. A high COI% resulting from inbreeding will in turn help bring forth and fix a trait within a particular bloodline; however, at the same time this is happening it can also cause an increase in the number of problem genes in a bloodline. Sometimes even though a dog looks to be free of serious genetic disease or disorders, there are less obvious problems that are starting to happen that may not be noticed right away. Immune system problems will start to creep into a line as well as thyroid issues and eyesight and reproductive problems as well.

The following is an excerpt from an article in The Field magazine, published in the UK:

“It’s not unusual for the same stud dog’s name to appear several times on both sides of a dog’s five-generation pedigree.
It often takes some time for the impact of such inbreeding to become apparent. The pedigree of most flat coat retrievers includes a dog named Shargleam Blackcap, winner of Crufts in 1980. He sired 252 puppies from 47 litters, and many people believe it is his influence that has led to the high rate of cancer in the breed today.
It’s a proven fact that most dog health issues are caused by recessive genes, so if one dog sires too many of the next generation then those recessive genes will meet up when half-siblings and other descendants are mated. Nor does it matter how healthy the stud dog is, as reduced genetic diversity will eventually lead to the familiar problems of inbreeding.”

To read the complete article found in The Field click this button:

This doesn’t mean we shouldn’t line breed but that we have to be very careful and selective with the choices we make and also know as much as possible about the dogs that we are going to use in our breeding program as well as their ancestors.

Below is some examples of COI% and what type of crosses they relate to:

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

We feel the emphasis needs to be on breeding setters with instinctive working abilities that possesses excellent temperament and health with a low COI %.

Over the 30+ years that Tom bred his setters he was more concerned with the working ability of his dogs in the grouse woods versus breeding to a dog that won a national championship in a field trial. He bred for dogs that could hunt with him and for him and that possessed the natural instinctive ability that is needed in a dog to work a grouse.

In the end because of the way that Tom bred his dogs we have a bloodline to work with that has a very low COI% and possess that natural close working ability needed in a grouse dog. Besides having the traits, we need for hunting they also possesses a more laid back manner which is great as a family pet. However, don’t be fooled when it is time to hunt they are no slouch and are driven to locate birds and to work with and for their owner. There never is a guarantee that there won’t be problems in any breed but having a low COI% is just one more responsible way to try to help prevent problems that might arise in the future of any dog.