Understanding How to Measure Genetic Diversity is Important for Curly Coated Retriever Breeders.
Updated: Aug 30, 2018
When breeders of a rare breed try to increase the genetic diversity of their stock, it is important to use tools which accurately measure diversity.
Several curly coated retriever breeders have developed an interest in increasing the genetic diversity of the breed--an effort I wholeheartedly agree with. But some of these efforts are actually contributing to the loss of diversity because of confusion or a misunderstanding of how to assess diversity.
One breeder extolled the virtues of a curly coated as a important breed contributor because the dog has no common ancestors in his first three generations. Unfortunately, having no common ancestors in the first three generations does not indicate great genetic diversity. What a shame if other breeders or puppy buyers believe a curly with no common ancestors in the first three generations is somehow more genetically diverse than the rest of the breed. This type of misunderstanding could lead to more inbreeding, not less.
First of all, truly accurate genetic diversity cannot be measured by breeding coefficients. An inbreeding coefficient is merely a probability chart predicting the influence of each ancestor on a particular litter. The most accurate measure of genetic diversity right now involves DNA testing.
But let's indulge this breeder referenced above who uses a THREE generation pedigree as a basis of claiming a dog is genetically diverse. Wow--pretty sure most curly coated retriever breeders/fanciers will immediately understand the fallacy of using THREE generations to measure a dog's genetic diversity.
Let's examine the pedigree of one of the most famous and revered curly coated retrievers in history--Darelyn Rifleman. This dog is an ancestor of probably 99.9999 percent of every living curly today. I believe there are only about 7 living dogs and maybe 2 dogs with frozen semen who don't have this dog in their pedigree. (I could be wrong--if you have a curly coated retriever who doesn't have this dog in the pedigree, I would LOVE to hear from you.)
So let's look at "Manny's" 4 generation pedigree.
Look at the notation in the top right corner "Coefficient of inbreeding." Rifleman only has an inbreeding coefficient of 3.52%, which is excellent for a rare breed!
But now let's look at TEN generations of Manny's pedigree which is the minimum number of generations most geneticists recommend for calculating inbreeding coefficients.
Big difference between 4 and 10 generation analysis, isn't there? His inbreeding coefficient is 23.71%. The jump in the increase of inbreeding when we examine more generations is because there were very few foundation dogs used to establish the breed. Many dogs were lost to breeding during the Second World War. Breeders worked with what they had to try to bring breed numbers back up.
When Rifleman, who himself had an inbreeding coefficient higher than 20, was so very successful in the show ring and as a generally great dog, many breeders bred to him.
The 4 generation coefficient of inbreeding on Manny is just 3.25%. The 10 generation coefficient is 23.71%. (And it would likely get higher the more generations we calculated.)
So, you can see that using a 3 or 4 generation pedigree to assess inbreeding just isn't prudent or accurate.
A more thorough examination of the pedigree of a curly who has no common ancestors in three generations, we find her nine generation pedigree analysis shows a 70.5% ancestor loss and the ancestor contributing the most blood percentage is Rifleman, even though he doesn't appear in her pedigree until the 6th generation!
There are many examples of curly coated retrievers like this. One pedigree analysis of a litter born in the U.S. indicated a dog who didn't appear in the pedigree until the 5th generation contributed 39.7% of the blood or more than the dog's grandparents.
There is nothing wrong with seeking genetically diverse breedings but we all need to be judicious in our claims and research. We may all need to beef up our knowledge of genetic diversity if increased genetic diversity is our goal.
Genetic diversity is unlikely to be achieved by pedigree-based breeding. In a seven puppy litter, there might be 5 who are very closely related and two who are genetic outliers. All puppies in a litter don't look or perform exactly alike because they inherit different genes than their siblings. A pedigree-based breeding program does not include the very important fact that two brothers may have different genetic codes.
The only way to truly measure genetic diversity is by DNA analysis. That would mean collecting DNA samples from hundreds of curlies from all the different countries. Could it be done? Probably pretty easily.
One of the best programs appears to be the University of California-Davis' Veterinary Genetics Lab. Many breed clubs are starting to enroll their breeds in the UC-Davis project. Here is a link to the Poodle Club of America's website regarding their diversity project: http://poodlediversity.com/
Another interesting website is that of http://betterbred.com. That website has a free class on the UC-Davis genetic diversity project.
Best of luck with your breeding and kiss a curly today.