Evaluating a Purebred Dog

Reducing Your Risks. Now that you know the two biggest risks of getting a purebred dog are, (1) creating a mismatch between a breed's inborn characteristics and what you want in a dog and; (2) the significantly increased possibility of getting a dog with a genetic disease, let's discuss how to reduce these risks. To reduce the chance of creating a mismatch, we will talk about the advantages of the Breed Selector software included with the eBook. To reduce the chances of getting a dog with a predisposition to a genetic disease, we will discuss two things. The first of these is, how to determine how much inbreeding has been done to produce your dog. The second is the health testing available for purebred dogs that can be used to identify various genetic abnormalities. These topics will be presented in the remainder of this chapter with the inbreeding and health testing, occurring first, then followed by using the Breed Selector. The effect on your risks of where you get your dog is described in Chapter 5 which talks about the many sources for your dog. Measuring Inbreeding If your dog has a written pedigree, it is possible to measure inbreeding in your dog's line. Wright's Coefficient of Inbreeding can analyze the line and give you an estimate of how inbred your dog is, based on how closely his ancestors are related. Wright's Coefficient of Inbreeding (COI) requires a complex mathematical formula to compute and is most easily performed by a piece of software specifically written for that purpose. A number of companies produce software marketed to breeders to assist them in their breeding program that compute the COI, but they can be expensive. However, a free tool that is available to compute Wright's Coefficient of Inbreeding can be found at FSpeed. You can only determine Wright's Coefficient of Inbreeding if your dog has a written pedigree extending back more than six generations. For the best results, you should analyze the pedigree eight to ten generations back in order to get a sound analysis. However, most AKC pedigrees only show three or four generations so in order to use this tool you will most likely need additional information about the dog's ancestry. If you are working with a reputable breeder, (more about this term in Chapter 5) they may be willing to help you obtain the information you need, or better yet, they may have already computed this information. Otherwise, you may need the help of the breed registry where the dog is registered. The Coefficient of Inbreeding. The Coefficient of Inbreeding, or COI, is expressed as a percentage. A COI of up to 5% is considered low and means that the dog is unlikely to have matching defective genes. Many purebred lines have a COI of 12% to 14%, while some lines have a COI as high as 20% to 40%. These dogs are statistically much more likely to have genetic diseases due to defective gene pairings and are also more likely to display inbreeding depression. A dog bred to its grandparent would have a COI of 12.5%. Dogs with a 25% COI, or higher, are genetically the same as a sibling-to-sibling breeding. Breeders that 'line breed' over a long period of time may create lines with these high COI percentages, even though they don't perform close inbreeding. The results of linebreeding over time are the same as in close inbreeding. To practically qualify what this means, one estimate is that a dog with a COI of 5% will live three years longer, on average, than a dog with a COI of 35%. This means that many purebred dogs will have a measurably shorter lifespan, as well as experiencing the other issues related to inbreeding, which can include genetically-based illness, suppressed immune systems, and unusual temperaments.