So, Coefficient Of Inbreeding....What Is It? And Why Is It Important To Know?

I had a prospective puppy buyer ask me what was the COI of this litter? I told her the genetic COI because that was what I had. She said she was looking for a very low COI because her vet told her the reason her last two dogs died of cancer was due to the breeder breeding dogs too closely related. That conversation started me down a rabbit hole that has kept me digging for many weeks. In this post, I will try to explain what I have learned about COI and why it is important for prospective puppy buyers to know what questions to ask when interviewing breeders of puppies they are interested in bringing into their home.

COI is a measure of how inbred an individual dog is. In other words, how many common ancestors in the puppy's lineage. If the common ancestors are in the first few generations, the COI will be higher. Also, if there are a lot of common ancestors in the puppy's pedigree, the COI will be higher. It is expressed as a percentage. AKC recommends breeders strive to keep the COI for litters under the average COI for their breed. Why is this important for breeders and owners?

A dog with a high COI can be at greater risk for health issues. That does not mean the dog will be unhealthy, just that if there are health concerns in the common ancestors in the puppy's pedigree, then the puppy may be more likely to be affected by those health concerns. In other words, let's say a breeder chooses to breed female dog "X" to her grandsire because said breeder wants to concentrate a certain trait in her puppies, if "X" and grandsire are healthy individuals with ancestors who lived long, healthy lives, the risk of health issues isn't necessarily higher than your average dog. However, if "X" and/or grandsire have a history of some health issue in their ancestry, then the risk of the puppies being affected by that health issue is much higher than your average dog. Why would a breeder risk that?

Because, there is no better way to establish certain traits within a pedigree than to linebreed. However, a good breeder will weigh all the risks against the benefits. Usually, the breeder will have a great deal of experience and knowledge with the pedigrees she is linebreeding. Hopefully, said breeder will have an understanding of any health issues that have occurred in the ancestors of both dogs and whether they did, or did not live long, healthy lives. When a breeder uses linebreeding carefully, it can be a great benefit to her kennel. However, we don't know the exact effects of a linebreeding even under the most thoughtful planning so there can always be unforeseen circumstances. And sometimes, a breeder doesn't know what she is doing and linebreeds without the indepth knowledge required to minimize the risks. So, why would someone risk buying a linebred puppy?

If a prospective puppy owner likes a certain type of dog, maybe they want to show, or enter field trials, and that kennel has been successful with their puppies in the activity the owner is interested in, the owner might be willing to take the risk and purchase a linebred pup from that kennel. That puppy buyer is trusting that the breeder has done their homework and made a decision that will minimize the risks as much as possible. Also, most ethical breeders have some sort of health guarantee for puppy buyers just in case the unforeseen happens. Then other buyers may not understand the increased risk that comes from purchasing a linebred puppy. Maybe they don't even know the questions to ask the breeder. They just want a puppy and they "fall in love" or the price is right and the purchase is an uninformed decision. Those are the folks who can be hurt the most by a breeder who is not making good breeding decisions. So, what should you know before you commit to buying a certain puppy?

A well informed puppy buyer will have:

1. some idea of what the COI is,

2. how it is calculated,

3. whether the puppy they are interested in has a pedigree based COI or genetically based COI.

Historically COI has been calculated using pedigrees from the sire and dam of a litter. So most of the COI averages you will see reported are pedigree based calculations. Most folks want to see a COI calculated from at least 10 generations of ancestors. Make sure you ask your breeder how many generations they used to calculate a pedigree COI. Unfortunately, AKC does not have a COI calculator, so looking up the pedigrees and inputting the data must be done manually. I can tell you....it is very time consuming! Some people say that COI is not important because the COI for most litters is inaccurate. One reason for the inaccuracy may be that there are so many errors in registered pedigrees. Without the availability of genetic testing sometimes the wrong dogs were reported to have sired the litter. Whether intentional or not, that would make the COI irrelevant. Another reason pedigree based COI calculations are not very accurate, is that only common ancestors across pedigrees are used for the calculation. The common ancestors within the dam's or sire's pedigree are not taken into account. Therefore, the COI could be grossly under estimated. Also, to get a true idea of the COI based on a dog's pedigree, you would need to go back to the founding members of the breed which isn't often done, that is why the COI is an estimate. Many breeders now prefer to use a genetically calculated COI because it is far more accurate than a pedigree calculated COI.

Genetic COI can be calculated for each individual in a litter and is a very accurate picture of that individual's percentage of inbreeding. Genetic testing can also give us a picture of what genes and traits are concentrated in an individual. Of course, the average puppy shopper, and even many breeders, will not know how to decode all of the information found in a genetic test result, but there are organizations that can help with that. Also, we do not have genetic tests for all canine health issues so we cannot test for every health issue that affects dogs. Even without complete understanding of genetic test results, a puppy buyer can get a good idea of the health of a puppy from the genetic COI.

For instance, the puppies from our current litter have a genetic COI ranging from 9%-16% with most of the puppy's at 11% and under. What does that tell a prospective puppy

parent? The average genetic COI for Labradors is 16%. Therefore, all of the puppies in this litter are at or below the average for Labrador Retrievers. Also, both parent's and all of the puppy's came back clear for all of the health issues the genetic tests screen for. So, a Montana Skies Labrador's puppy family can be fairly sure they have a healthy puppy that, if managed well, should live a long, healthy life.

How can you, the prospective puppy parent, use the COI and genetic test results to help you find the puppy of your dreams? First, find a reputable breeder that is conscious of canine health concerns and willing to answer your questions about their puppies. That may be harder than you think, but there are many good breeders out there who are only too happy to talk healthy puppies with you. Once you find a breeder, or two, or three, make up a list of questions you would like to ask them. Include all of the general questions about registration, color, temperament, etc. and then make sure you add the following:

1. What kind of testing have you done for the sire and dam?

2. What lab did you use?

3. What specifically were the parents tested for and what were the results?

4. Ask to see a copy of the results.

5. Do they offer any testing for the puppies?

6. What is the COI for the litter?

7. Was the COI calculated by pedigree or genetically? If pedigree, how many

generations were used?

8. What is the average COI for the breed?

A good breeder who loves their dogs and is proud of the hard work they put into breeding the best puppies they are capable of will be more than happy to answer all these questions and offer more information according to their experience. Take the time to find a good breeder that you trust. Hopefully, one who will provide a lifetime of support for you and your puppy. After all, by purchasing a puppy, you are making a 12-15 year, or more, commitment. It only makes sense to take some time and make an informed decision. Then you can spend the next dozen or so years enjoying your new family member.