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  • Breeding for Inherited Traits: Avoiding Disease

    I thought I'd post up a couple of links & a couple of
    quick comments about "genetic" disease (as people
    say), that is disease that is directly inherited and/or
    inherited with a strong genetic component, so that
    avoiding disease becomes, in part, a matter of
    breeder choices as, at least partially then, under
    a breeder's control. There seems to still be some
    HUGE misconceptions out there about inherited disease.

    Just starting with the term 'genetic disease'---all disease in a
    sense is genetic, as it all involves genes. And it's just not the
    case that disease either can be split into neat categories of
    "genetic" (inherited) and "environmental." Such categories don't
    exist in the biological world really & this isn't anyway what is a
    breeder's focus when chosing bloodstock & planning breedings.

    It's worrisome I see now websites touting outcrossing as some
    formula for health--just like you used to see linebreeding offered as
    some formula for type. Such generalizations and "recipe breeding"
    just don't work: you have to make yourself clearly & completely
    aware of not just sire & dam, but the family, writ large, of the dogs
    you are dealing with. That's why it's sad to see someone admiting
    to type problems, saying they are importing dogs to outcross as they
    "believe" it confers better health (and/or temperament). Breeding to dogs
    with admitted shortcomings that you have never seen is no way to end
    up with good dogs--no matter how you define . And such a "recipe"
    isn't going to confer health anymore than breeding any relative of a
    famous dog to another of the same family is going to guarantee type.

    What people may not know is there is such a thing as *outbreeding
    depression* just like there can be inbreeding depression. With inbreeding
    depression, typically you will see two sorts of results. On one had recessive
    traits come to the fore, be they odd colors or things like Wobblers & mega.
    The other thing you see is a general tendency to smaller litters, smaller size,
    & lessened fertility as well as a general sense of lack of thrift. IOW you end
    up with "poor doers"--dogs who are fragile or fiddly--when you depend on
    linebreeding too much, do it indiscriminately, and/or are not "minding the
    store," as in knowing what skeletons lurk in your family closet. When things
    like this start to accumulate, you simply have to "let some air in" a closed
    pedigree and/or you have to be more selective in what animals you are
    choosing, not using some dog simply because he finished or his dad did well,
    especially if having to rationalize a dog who did well in one way (say showing)
    while he has other problems that are line-related. Linebreeding isn't something
    to do blindly.

    But some diseases, particularly complex traits like involve CHD (hip dysplasia)
    you can actually get by outcrossing. Why? Because one you are "breaking up
    a good set" of genes that has been working for you and your dogs. Secondly
    you are importing, wholesale, in an outcross, a set of foreign genes at times,
    and they may also work on their own, but not when they are broken up &
    mixed with yours. These sorts of situations are called THRESHHOLD
    DISEASE & the gene expression used is "cumulative traits." Things like
    size in a line, head type, organ and joint structure are very often a result
    of such cumulative traits. IOW they are only the result of a bunch of the
    "right" genes coming together, not any one "good" or "bad" gene. With
    cumulative traits the best breeding strategy is typically about avoiding
    extremes: You stick with the middle & don't call moderate mediocre,
    as by avoiding extremes, you collect up the most of the genes that work
    well together, giving you what you want to keep seeing. That also means
    you recognize every dog isn't going to always be ideal to be useful to
    your breeding program. What I mean by that is that, for example, if
    you have a family of dogs who are all checked and all passing OFA,
    you avoid dogs then that fail and/or who develop CHD (the extreme),
    but you can use dogs who are not Excellent, as they likely have nearly
    the same set of genes for this cumulative trait. Or, another example,
    you want good size, so you use some moderate sized dogs, but not
    really tiny little bitches. Avoid extremes, but don't go overboard looking
    for "just the right" (ideal) dog is the idea with cumulative traits. Outcrossing
    in the case (and temperament is another area of complex inheritance) is
    arguably more likely to be hurtful than helpful, unless you really know that
    other family well indeed. Different strategies for different genes.

    And the strategy is again different for traits that are hybrid traits (like
    Harlequin color) or X-linked (like Dane DCM). You cannot just make
    blanket statements (linebreeding or outcrossing is good or bad), or
    breed to "famous names" or "has health checks" bloodstock and
    expect success. There are so many new breeders out there, seems
    there are more & more everyday. And most anymore tend to be
    "independents" who may have purchased a dog or bitch here or there,
    but are not aligned with any one breeding program or have a specific
    mentor. That can create problems & result in folks having to "learn by
    doing" by which I mean have a litter with problems that another more
    experienced breeder could have seen was a decided risk. Noone creates
    problems of any kind on purpose. But as the road to hell is paved with
    good intentions, in this world of dog breeding, ignorance has probably
    spawned more tragedy than pure evil.

    And doing disease screenings ("health checks") is great, but these tests
    also have to be used knowledgeably. For example, the OFA Cardiac does
    NOT screen for DCM or SAS. And doing a thyroid check without a TgAA
    is pointless on young breed stock, while doing an initial screening is fine,
    but it's no declaration that the same dog, when 4-6 years, is still thyroid normal.
    A CHIC dogs with all passes can later gets thyroid disease or comes down
    with Addison's, just as a dog who is "healthy" can mean nothing more than
    the owner isn't unhappy with the dog, and doesn't mean he doesn't have
    things that would trouble you. And a lot of checking for disease, is considering
    relatives. A DCM carrier bitch is never going to show any signs of what she
    inherited & will still pass this deadly disease on to her sons & daughters.

    We cannot be "one trick ponies" when breeding--we must "multi-task" in
    the sense of juggling all the issues (health, temperament, type, structure,
    gene cleanliness) involved. And we need to sort this, as no dog is going to
    have it all. So you have to prioritize. And for disease, this is going to mean
    strongly selecting against inherited diseases that are (a) deadly, (b) serious &
    chronic, (c) costly to manage. And a priority has to be set to screen against
    adult-onset diseases, as these are likely to "show" after you have bred. Esp.
    in Danes where some of our large problems *do* only show in the middle
    years. So, here again, shows you how important it is to first (1) know your
    pedigrees as more than names & titles, and then (2) be knowledgeable about
    what is the best strategy of control for each kind of inherited disease.

    To that end, here are some links on how to assess the risk & do a risk: benefit
    analysis and relative risk assessment of various problems (below). And I am
    ALWAYS available to help with these relative risk analyses to those that
    want a consult. This is done with full confidentiality of course. Links:
    http://www.gdca.org/healthandwelfare.htm
    http://www.chromadane.com/inherdis.htm
    http://www.chromadane.com/VARGASeriesArticles.htm
    http://www.chromadane.com/BreedersCorner.htm
    http://www.chromadane.com/practicalgen.htm
    http://netpets.com/dogs/reference/genetics.html
    Best Regards, JP Yousha
    Chmn., Health & Welfare, GDCA
    www.gdca.org/healthandwelfare.htm
    danehealth@gdca.org

  • #2
    RE: Breeding for Inherited Traits: Avoiding Disease

    Great article and links! Thanks for sharing this.

    Kim E

    Comment


    • #3
      RE: Breeding for Inherited Traits: Avoiding Disease


      Breeding is difficult? From reading many on this forum I thought all you had to do was breed two champions that had all of the health tests.


      Duane with
      Ch. Geisha, Harley and Iris in
      Saginaw Michigan
      Great Lakes...Great Danes
      http://duanemorgan99.tripod.com/DuanesDanes/

      Comment


      • #4
        RE: Breeding for Inherited Traits: Avoiding Disease

        Thank you JP for a very insightful post.

        Here on DOL we are lucky that there are individiuals in the dane community who care and continue to educate. Breeders who have worked so hard to acheive greatness and who hope that by repeating themselves for the upteenth time...someone out there is listening and will take to heart what they say.

        Comment


        • #5
          Breeding a male with Addison's in the line

          Hi Everyone,

          I am a newer breeder and and I am looking at a stud dog to breed my bitch too. I have just found out that 3 of his dams siblings were diagnosed with Addison's and his grandsire passed away due to the disease. I would like others thoughts on continuing a line that you know has Addison's in it. Is this irresponsible or common practice. As I stated I am newer to breeding and I want to make sure that I am making a decision that is responsible.

          Thanks for your input!

          Comment


          • #6
            You should really post this as a new topic.

            Quickly though, do you have a mentor for breeding? Who is helping you get started?

            I am going to assume you are doing the proper steps, showing and finishing dogs, only breeding health tested dogs, etc.

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