How High is Too High?
A 5-minute read about evaluating COI magnitudes.
From Part I: The 10% rule is a historical calculation of risk developed before genetic testing was available to breeders. It’s a mathematical statistic that gets routinely misapplied, and should never be used as a stand-alone measure of the quality of any given breed, litter nor dog. The number of generations used in the calculation and unknown/missing dogs in a pedigree can both influence a COI calculation, typically lowering it and producing an understated level of risk. If you’re not using a 10-Generation COI calculation the 10% rule isn’t applicable. Period.
Now we want to talk a bit about COI magnitude. A “low” 10-Generation COI as defined by the Institute of Canine Biology, is <5%. A COI that low indicates a very small level of risk of inbreeding depression. BUT, a COI that low will reduce the likelihood of puppies being consistent with a breed standard…assuming the parents meet the breed standard, of course. Breedings resulting in a “high” 10-Generation COI, defined as >10%, will likely result in a loss of hybrid vigor and could have an adverse effect on the overall health of a breed over time. HOWEVER, a high COI will more consistently produce offspring that look and act like their parents than a low COI.
A purebred dog/breed is the result of generations of litters over decades of selective breeding such that all the dogs within the breed pretty much look alike and behave similarly. That’s the good news. The bad news is that selective breeding reduces the gene pool by weeding out dogs that don’t “look right.” An off-color dog might have other traits/characteristics that would be beneficial to keep in the breeds gene pool. Dogs have ~20,000 different genes, many of which are recessive, and thus not outwardly apparent. Complicating things further, most genetic traits are multi-allelic, so breeding for a particular color, for example, may impact other inherited traits. Getting rid of “unwanted genes” helps maintain a breed standard, but it is risky, especially with genes that impact multiple features within a breed.
Let’s look at the Gordon Setter. When most folks think of a Gordon Setter they visualize the current breed standard…a black dog with tan pointing. But historically the Gordon Setters were black, liver, red, black-and-white or tri-color. Even after ~80 years of selective breeding for the black-and-tan colored coat there are still a few off-color, or mismarked, Gordon Setters whelped every year. A liver coat, for example, is an automatic disqualification for breeding in the US, even if the dog is structurally perfect with respect to the breed standard, is very cooperative, hunts like a beast and has a pleasant demeanor. In that hypothetical example plenty of “good” potentially goes out of the gene pool with the “bad.” Not a criticism, just a statement of fact. Conversely, the genetic profile that makes up a black-and-white Gordon Setter often comes with a predisposition to deafness. In that case the gene pool benefits from selective breeding for the black-and-tan color.
According to the Institute of Canine Biology there are only ~20 purebred breeds with an average genetic COI <25%…the rest are higher. A recent UC-Davis study concurs, stating that the average inbreeding based on genetic analysis across 227 breeds was close to 25%. A deeper look into these studies indicates that only ~1/3 of the breeds included were “hunting breeds! That notable clarification aside, the Genetic-COI of purebred dogs in these studies is between 20% and 80%. Yup, 80%…the Norwegian Lundehund has a Genetic-COI of ~80%! By comparison, the hunting breeds included in these studies…GSP, Lab, Golden, Pointer, Wirehair, Beagle…all have a Gen-COI of ~20%. One other important thing all of those breeds have in common are very large populations (100,000+) which can help in preserving genetic diversity while at the same time maintaining a breed standard. By comparison our Castiron Kennels Picardy Spaniels have a Genetic-COI range of 19-22%, and the global population is only ~2,200 dogs.
Circling back. “How high is too high?” It’s breed specific and depends primarily on the average Genetic-COI of that particular breed. Even though the number of Picardy Spaniels that have been genetically tested is pretty low, let’s assume the Picardy has a breed average of ~20% Genetic-COI. Our foundation bitch, Cleo, has an 8-Generation COI of 7.7% and a Genetic-COI of 20%. Our foundation sire, Manny, has an 8-Generation COI of 8.9% and a Genetic-COI of 19%. Qualitatively this looked like a good breeding in terms of keeping the COI low. Quantitatively it looked good as well using Cleo and Manny’s 8-Generation COIs with virtual breeding software. The 8-Generation COI estimate was 8.2% for their offspring. Genetic testing of Argos, one of the male puppies whelped from that litter, showed his Genetic-COI is 20%. Mission accomplished. BUT, trying to accomplish the same with a breed having a higher Genetic-COI average may not be possible. With the Norwegian Lundehund, for example, a breeder may be trying to keep a litter at or below a Genetic-COI of 80%.
There’s another important facet when wrestling with “How high is too high?” conundrum. Breeding logistics. Outside of Manny, there were only a handful of sires in the US that were options for breeding Cleo. Quebec had a couple of possibilities, and Europe had many more options in terms of potential sires. Even though the world is a much smaller place than it was when COI was introduced, it’s still not that easy nor financially practical to ship semen or sires from Europe or Canada to the US. We brought Manny in from France in hopes he would become our foundation sire. Fortunately that worked out. In addition to being a solid hunting companion he’s produced some great pups. He’s retiring effective 2023 and we are now evaluating sires for our youngest female, WildKat Whiskey. More on that in our upcoming conclusion to this post: COI Alone is Not Enough
Ric, Ellen and their 4 Picardy Spaniels live in New Glarus, WI just 25 minutes southwest of Madison. A lifelong hunter, Ric has trained and hunted Small Munsterlanders, Gordon Setters, and for the past 6 years Picardy Spaniels. Ellen has an extensive background in animal genetics and a PhD in Reproductive Physiology. She bred and trained Greater Swiss Mountain Dogs prior to Picardy Spaniels.