What is COI?

The Coefficient of Inbreeding (COI) is a measure of the level of inbreeding of a dog. To be inbred, a dog must have one or more common ancestors on both sides of the pedigree. All dogs are inbreed to some degree (that is how breeds are formed), but they will vary in how many generations it takes before the common ancestors appear. Genes come in pairs - one from the sire and one from the dam. The COI is the probability that both genes at a locus were acquired from the same ancestor (one through the sire and one through the dam). Inbreeding has both good points and bad points. See the reading list below for further study.

If we go back far enough the number of ancestors required will exceed the number of dogs that were alive at that time. When John Armstrong did his work, most Standard Poodles had about 350-400 ancestors in a 10 generation pedigree (ranging from 79 to over 900 out of a possible 2046). Today we have seen those numbers increase to the 500-800 range with some achieving numbers near 1200. Although this sounds good, it is mostly achieved by the bottleneck in Standard Poodle now being more than 10 generations back. If 15 or 20 generation COIs are run, there does not seem to be much change in the COI of the overall Standard Poodle Population. The inbreeding coefficient (COI) estimates the probability of receiving two identical copies of a gene from an ancestor common to both parents.

Expected Values

Lower COI values are considered "safer" and less likely to exhibit inherited disorders. However, when the problem gene is widespread in a breed, a dog with a low COI may be just as likely to have the disorder as one with a high COI. It is important to know as much as possible about the dogs in the pedigree, regardless of their COI.

What is considered low is based on the breed average which varies from breed to breed (and varies with variety in Poodles). In Dr John Armstrong's study the average COI for Standard Poodles was about 15%. And breeding a black or white/cream Standard Poodle with a COI of under 10% is very difficult unless you introduce another color. Most black and white Standards are as closely related as first cousins -- because they all have Wycliffe Jacqueline and Annsown Gay Knight of Arhill as pseudo-grandparents. This means that accurate COI calculations really have to go back enough generations to reflect their contribution. Remember that a dog with a low COI at 10 generation may have a very high COI at 20 generations because of the bottleneck of Gay Knight and his sire, Annsown Sir Gay.

Reading List:

Genetics of the Dog; Willis; 1989

Genetics for the Animal Sciences; Van Vleck, Pollak, & Oltenacu; 1987

Practical Genetics for Dog Breeders; Willis; 1992

Diversity in Poodles web site; Armstrong; 1998

How to Breed the Perfect Poodle; video of Dr John Armstrong at the PCA Foundation Seminar, June 2001; available from Allen Kingsley, 3311 Kingfisher Lane, Denton TX 76201; (Great talk, he uses real pedigree data in explaining concepts)

Pedigree Analysis: How your breeding choices manipulate the genes of your dogs; video of talk by Dr Jerold Bell at the PCA Foundation Seminar, June 1998; available from Allen Kingsley, (Excellent talk. He uses Poodle examples in discussion of COI and relationship coefficients.)

Breeding a Great Poodle; 2 videos of seminar by Dr George Padgett at the PCA Foundation Seminar. Available from Allen Kingsley, address above.