![]() It can just as easily be done for dogs as well, and Cavaliers are a perfect candidate. Animal breeders have been doing this for hundreds of years to produce quality animals that can be nearly identical, with inbreeding levels in the single digits. We do know how to do with without losing breed type. We know that we can only restore health by restoring genetic diversity. There are plenty of other breeds in similar shape, but what matters to those that love Cavaliers is whether it can be saved. In fact, this is where Cavaliers appear to be now.Ĭavaliers are in deep trouble. Inbreeding will continue to go up over time, the small genetic differences between populations will disappear over time as genetic diversity declines, and eventually you will no longer be able to produce healthy animals. You might temporarily reduce the incidence of some specific nasty mutation temporarily in a part of the population, but everybody is in the same genetic pot. No amount of selective breeding is going to improve the health of this breed. The problem with science is that it's true even when it's not what you would like to believe. You can see from this that health testing in Cavaliers is really not accomplishing anything except costing you money. ![]() ![]() But when all the dogs in the population are closely related, the average inbreeding of a litter is 40%, far above the 25% risk you're trying to avoid. ![]() ĭNA testing allows us to test for carriers of mutations so that we can avoid this 25% risk of producing affected animals. The level of inbreeding in Cavaliers is way - WAY - higher than that. Most people would not do a breeding of two littermates, but the inbreeding data show that in fact most breedings are between dogs much more closely related (i.e., genetically similar) than littermates. (I have included links below to download the jpg file so you can blow it up big enough to read the breed lavels.) Remember, 25% inbreeding results from a full sibling cross from unrelated parents. The black lines on the graphs are at the average level of inbreeding in Cavaliers in those two studies. It really doesn't matter how you sample the population, the estimate of average inbreeding doesn't vary much. This reflects the high level of inbreeding and genetic similarity among the dogs. For two unrelated datasets, of very different sizes, the level of inbreeding in the Cavaliers was essentially the same. dataset (the red graph below), the inbreeding based on DNA for the Cavalier averaged 42.1% (black line), and for the Bannasch et al. I rounded up the data for two studies, one that included 10 dogs per breed based on US (mostly AKC registered) dogs Dreger et al (2016), and another that included data for 455 Cavaliers registered with the FCI, AKC, UKC, or the Kennel Club ( Bannasch et al., 2021).įor the Dreger et al. We said that a full sibling cross resulted in inbreeding of 25%. The problem with Cavaliers is that their level of inbreeding is extraordinarily high. For a recessive mutation in the genome, that is a 25% risk of producing an affected animal. Full-sib pairings produce offspring with inbreeding of 25%. In most cultures, that disease risk is deemed too high, and these marriages can even be banned.įor half-sib pairings, the inbreeding produced in the offspring is higher, averaging 12%. For recessive mutations, that is also a risk of genetic disease at the same level of 6%. This is because your children would be inbred, at a level of 6.25%. In most societies, marrying your cousin is frowned upon. Eventually closed populations like this have such high levels of inbreeding that they are wrecked by health problems and infertility, and they simply go extinct. So the variation in the genes in those original 8 dogs is gradually lost over time. Furthermore, gene variants are lost every generation through selective breeding and also just by chance. Over time, the animals in a closed population can ONLY become more closely related (genetically similar) to each other. It's a bit like trapping you and your immediate family on an island from which there is no escape. There are no "outcrosses" here every dog is closely related to every other dog. Also, because the stud book is closed, dogs can only breed to related dogs. If the stud book is closed, then all the genes the breed will ever have come from those few dogs. I've seen numbers of 6 and 8 let's just call it a handful. The Cavalier King Charles Spaniel was founded on only a handful of dogs.
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