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Thread: Anyone know?

  1. #1
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    Default Anyone know?

    If you have scanned your dogs before breeding on them - and they have no sign at all of SM - does that mean that the puppies not will have SM?
    Christina, with the dogs Chanel and Freja.

  2. #2
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    Hmm, if both parents have clear MRI scans for SM then you would have a much higher chance of the litter being clear too. HOWEVER, the one thing that the scan CANNOT tell you, is if they are carrying the genes that cause SM recessively or not, 2 MRI'd clear dogs could both be carrying those genes and produce affected pups, this is the biggest gamble with breeding really, you have to be really sure of all the dogs for at least 5 generations back on both sides as they will hugely influence what your litter will inherit. Also if you are line-breeding then you have a much reduced gene pool to play with, but if you are outcrossing you will increase the potential gene pool but be very wary of what you might be bringing in, breeding is a huge game of chance at the end of the day!!

    Hope this Helps?
    Cathryn
    Cavaliers leave pawprints in your heart and hair on everything else!!
    RE-LIVE YOUR CHILDHOOD THROUGH YOUR KIDS, THE TOYS ARE SO MUCH BETTER THESE DAYS!!

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    does that mean that the puppies not will have SM?
    The short answer as Cathryn notes, is NO. This condition is so widespread in the breed now that genome researchers could not even find enough totally clear cavaliers (clear of the malformation that causes SM, and SM itself) to form a crucial clear genetic group that would help them find the responsible genes in affected dogs. Almost every cavalier has the malformation, which causes the skull to be too small for the brain, in different degrees of severity. They have had to go to a totally different breed that also has SM in smaller numbers, Brussels Griffons, to find the clear control group for the very important gnome research now taking place in Canada. You can read more about where this research stands here.

    What that means is that as with MVD the genes for the condition are likely permeating nearly all cavaliers so almost any mating is going to pass along some of those genes. What isn't understood yet is the mode of inheritance -- if it is a polygenetic trait (eg requires several genes to combine to produce affected dogs) as researchers believe, then which genes or possible environmental influences trigger more severe cases?

    What initial research has shown is that A grade dogs -- no syrinx -- tend to produce almost no affected and symptomatic dogs, and the highest number of A graded puppies (though these have not been tracked across a full lifespan as this work is only a couple of years old now). Also, scans of family groups have shown that A grade dogs tend to be closely related to other A grade dogs -- find one A grade dog and you'll probably find others amongs parents or siblings or offspring. So scanning has enabled breeders to find other A dogs very successfully in the Netherlands (instead of just randomly scanning in the hopes of finding As), where they are very organised in doing such research (sadly no other breed clubs are pursuing this type of research at this time though the UK club is sponsoring research to get clearer breeding guidelines). There are known, affected offspring however from AxA matings but not many. Statistically this is always possible.

    Asymptomatic but affected dogs (that turned out to be D grade or eventually symptomatic) have so far produced NO A grade offspring and a significant number of low grade dogs.

    You can listen to a free podcast of Dr Clare Rusbridge explaining the condition and this research here: http://sm.cavaliertalk.com/rusbridge.mp3

    You can buy two CDs of all the talks (aimed at a general audience) at the recent conference on SM in cavaliers in Rugby, UK here: http://www.cafepress.com/cavaliertalk/4311456

    Personally, I would now want scan grades for both parents and to discuss overall breeding programmes before buying any puppy.
    Karlin
    Cavaliers: Jaspar Leo Lily Tansy Libby (foster) Mindy (foster)
    In memory: Lucy
    Cavalier SM Infosite:www.smcavaliers.com

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    Default Thank you!

    Thank you for your answer. It is very interesting to hear what you think about this question. I am not a breeder but what I now it is not common to scan before use a dog for breeding. (In Sweden) We are still only talking about the heart, eyes and knees.

    Is it common in your countries?

    Even if you can't exclude that scanned and free parents will have puppies that will have SM one day, it gives a very good hint.
    Christina, with the dogs Chanel and Freja.

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    No, it isn't common in the UK, US, Canada, Ireland or Australia, and indeed, meets a lot of resistance. The Dutch breeders have been the most active and are producing the most practical information.

    Recently Brussels Griffon breeders have become very proactive about this condition in their breed clubs particularly in Australia and the UK and have already organised support for screening and research even though their breed is far less affected.

    I would not be surprised if Swedish breeders eventually take a lead role in SM screening as they already have the most health-focused breeding requirements of any club, anywhere in the world. They are the only club to require basic health testing for registered dogs used for breeding registered puppies.
    Karlin
    Cavaliers: Jaspar Leo Lily Tansy Libby (foster) Mindy (foster)
    In memory: Lucy
    Cavalier SM Infosite:www.smcavaliers.com

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    "Asymptomatic but affected dogs (that turned out to be D grade or eventually symptomatic) have so far produced NO A grade offspring and a significant number of low grade dogs."

    Karlin, you give such sound replies that I usually just read, but I was a little confused when I read this part of your response. I though I'd clarify for others a little slow like myself.

    A 'D' grade dog paired with another 'D' will not ever produce an 'A' grade . . . but a 'D' grade dog paired with an 'A' can produce 'A' grade pups (and D's as well). This was how the Dutch initially started, because they did not have enough 'A's for A x A pairings. It is also the reason that the protocol allows A x D pairings. The loss in breeding population if every D grade was pulled from breeding, at 70% syrinx rate, would cause a huge bottleneck and create a mess of our breeds diversity if this was the route taken -perhaps raising the risk of many other yet uncovered difficulties cropping up.

    Of course A x A most consistently produces A grade pups, but I know the percentage I've heard tossed around on that is significantly lower than 100% of the time.

    For those reading and looking for pups, please keep in mind that a pup produced from an A x D pairing may end up with syrinxes but still has a significantly better chance of having no symptoms than a pup produced from a D x D pairing - as this problem seems to worsen generationally. Breeders using MRI are having to make breeding decisions not only for their own kennel, but for the good of the whole breeding population.

    I'm sure we'd all love to see no SM and no symptoms, but that is going to take some time, a lot of conscientious breeders, and probably a gene test.

    _________________
    Arlene and her three

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    Thanks for the post. I think on reconsideration that you have this right. I'll have to go back and check the podcast and my notes -- I had recalled that Clare showed no A dogs from any crossing with a D, but I may well be confusing this and that it was actually that no mating that DIDN'T include an A dog produced any A grade offspring. In other words a DxD or DxF. That's an important point.
    Karlin
    Cavaliers: Jaspar Leo Lily Tansy Libby (foster) Mindy (foster)
    In memory: Lucy
    Cavalier SM Infosite:www.smcavaliers.com

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    You are completely right! I went back and reread my notes and listened to the talk. Thanks for the clarification.
    Karlin
    Cavaliers: Jaspar Leo Lily Tansy Libby (foster) Mindy (foster)
    In memory: Lucy
    Cavalier SM Infosite:www.smcavaliers.com

  9. #9
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    Thanks for checking Karlin.

    For the original poster, and anyone else who really wants to delve into SM studying, it was mentioned in the winter newsletter that research is continuing into correlating head shape and SM - but this time not by simple observation as was used before (unsuccessfully). The researchers are checking out x-ray results and comparing them to MRI.

    So far (this is just initially) there seems to be some evidense that x-ray can give you some indication about symptomatic SM risk. The more domed headed, flatter back skulled Cavs seem to have more risk of symptoms (CM is an aggravant possibly?) Here are some links to some interesting pages about this.

    http://www.premiercavalierinfosite.c..._comp_page.htm

    http://www.premiercavalierinfosite.c...d%20Shapes.htm

    http://www.premiercavalierinfosite.c...d%20Shapes.htm

    http://www.cavaliercanada.com/docume..._Syringomyelia[1].doc

    I know if I were breeding I'd be keeping up on this ongoing head shape study. Even as a pet owner I'm very interested . . . but then I hope to breed in the future.

    The correlation between CM and SM is not always what it would seem, though, as sometimes even mild Chiari and a lengthy skulled dog will come up with SM (this is a gene problem after all), so for breeding purposes MRI is imperative.

    I have a Cavalier pet who shows no symptoms of SM, but I worry, so for myself, with MRIs here being $2500+ and impossible to book without a sick dog, I took an x-ray on my guy just to see where he stood by head shape. Now I'm quite happy that I took the big headed pup, even though my hubby still teases me about it!

    Arlene and her three

  10. #10
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    ...also just a point to think about as well,

    SM is progressive and onset can be at any time.

    No dilation one year can be quite moderate the next, likewise symptoms and a syrinx. Perhaps regular scanning on a 2yr period would be a good idea? especially for breeding stock. This would give a little more genetic history to work with as well?

    Alison.

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