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Re: Ryman Health?


The Ryman Setters Forum Forums Health Ryman Health? Re: Ryman Health?

#185
October Setters
Keymaster

    Robert,

    I don’t know if you can state a certain COI over which you run more risk- putting a precise cutoff level is probably impossible. For instance, 20% inbred to a single dog is quite different than 20% total from inbreeding to several different unrelated dogs. (Linebreeding is, by definition, inbreeding so I’m calling it what it is here.)

    The models show clearly how inbreeding has been a factor in the widespread health problems in all breeds, but Beauchat, and a lot of other people, make a serious error in logic by leaping to the conclusion that outcrossing is the answer to preventing health problems. Has inbreeding caused a higher incidence of health problems? Yes. Does it follow that you can you prevent health problems or eliminate them simply by outcrossing? No!

    A few examples:
    If you breed two dogs together that both carry an undesirable recessive gene will it make any difference in the offspring if the litter is inbred or outcrossed? No.

    If you inbreed to a dog that carries an undesirable recessive gene will you see more of that gene expressed? Yes. All inbred dogs are more homozygous at all gene locations (if the inbreeding worked as intended). So, more dogs out of the inbreeding will be homozygous for that particular recessive and therefore express it. At the same time, more will be homozygous for NOT carrying it.

    If a breed or line has a prevalent health problem caused by a recessive gene outcrossing will do nothing to improve the situation unless outcrossed to something that doesn’t carry it. If the outcross was done to another breed that doesn’t carry the gene you will have reduced the rate of occurrence, but you have not eliminated the gene. That will still require selective breeding regardless of whether you are inbreeding or outcrossing.

    The designer cross-breed fad has proved that outcrossing in and of itself does not reduce health problems. Those dogs are not healthier than the pure breeds they are derived from and as an added bonus they now show all the health problems from both breeds.

    Every experienced breeder I know says the same thing: Outcrossing is where they have picked up problems.

    The OFA sees this scenario a LOT: A breeder does an outcross with an OFA Excellent dog to another OFA Excellent dog. Both dogs are from lines that produce a low incidence of hip dysplasia. Unknown to the breeders of both lines, they each carry a small, but DIFFERENT, set of HD genes that aren’t enough to produce many problems… until they are matched up with each other. The combination results in a disastrous litter full of dysplasia.

    There is compelling evidence that homozygosity in the MHC (major histocompatibility) genes is associated with more immune system related diseases like allergies and diabetes. Extreme inbreeding can also cause inbreeding suppression, with lowered fertility and fitness. So, I am all for avoiding close and especially endlessly repeated inbreeding. My biggest complaint about what people like Beauchat promote is that it suggests a simple solution for breeders to follow that won’t by itself really do anything. Simple answers are appealing so everyone jumps on them. Plus breeders either deceitfully or ignorantly claim their dogs are healthy because they don’t inbreed, and therefore don’t need health clearances. There is at least one current Ryman-type breeder doing this, and the lines being used are notoriously bad for HD.

    Padgett’s book goes into great detail explaining why outcrossing is not the simple or logical answer to eliminating health problems, and how to actually DO get rid of them. “Genetics of the Dog” by Willis is old, but a good primer on genetics.

    Lisa

    PS: Here is the British version of the above TV program. It’s basically the same information but slanted more toward what is relevant to breeding.
    https://www.youtube.com/watch?v=h1jBrE0qxsw

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