Loading the Dice

The following essay resulted from a spirited discussion about inbreeding co-efficients, is it possible to have too much of a good thing, and related questions.



Commentator: There is a lot of controversy about how high is too high. Many geneticists believe very strongly in diversity being essential for optimum health, but breeders want to put a personal stamp on what they produce so tend to linebreed rather than outcross. I'd love to hear what others think on this matter!



The Witch: Wish Granted!



Here is the quick and dirty answer: as the coefficient numbers go up (meaning more inbred) the consistency of production in the get for the attributes you are breeding for also increases. In other words, the more inbred the litter, the more consistent the puppies are. However, the trade-off is that the higher the coefficient, the greater the chance of health weakening, if it is taken to extremes. This is not an absolute, there are healthy lines of dogs that are very inbred indeed, but over time as you continue to inbreed, you lose diversity in the histamine complexes and certain of the cascade antigen sets, and you begin to see problems inherent in this sort of depletion, such as poorer overall immune response and attendent allergies as well as other immune type problems cropping up. Some of these disorders can be weird, and some are deadly, such as rare cancers, etc. The overall increase of these disorders within the breeding population is not drastic, even in VERY inbred stock, but it is significant enough to warrant notice. This is the downside of inbreeding. There are other more obvious problems as well, such as the greater likelihood of meeting up with deleterious recessive genes in closely related kin.



However, it is a very fine line to walk, when you begin with the premise that ANY breed is a closed subset of genes, and that setting aside any gene set inevitably creates these kinds of problems to a greater or lesser degree. Linebreeding is the same sort of dilemma on a smaller scale, nothing more. The good news, which no one wants to focus on, is that it is very simple to fix these 'doubling' problems when they occur; a judicious outcross will fix almost anything in that regard. The bad news is that outcrossing will also muck up the consistency of the get; and you are right back to square one in a very few generations, with very inconsistent get.



A great deal of the issue hinges on that term, 'optimum health.' We all want to 'breed for' good attributes (like health, or good hips, or what have you) and 'breed away from' bad ones (like allergies or osteo) but the PROBLEM is, in order to do so CONSISTENTLY, you have to limit the gene sets. Which means: line or inbreeding. It is pretty much the only way to 'set' type, and that is the same whether the 'type' you are trying to fix is a particular type of head or a particular type of hip socket. So, to improve health we must outcross, but to optimize and 'set' the health benefits of strong dogs, we have to line breed on their stellar qualities. It is a pretty pickle...



So you see, line and inbreeding is not really the evil that many insist; if you are going to maintain anything of value you have to select FOR it...and that means AWAY from other things, and that ALWAYS means limiting the gene pool to a greater or lesser degree. The trick is to limit the genes for the good attributes while not losing the necessary diversity to maintain health.



I personally opt for once-out-twice-in (more or less, not particularly strict here) and if I am seeing too many problems that make me nervous (allergies, etc) I go twice-out instead. It has seemed to work pretty well for me over the long haul. I think that too many people believe breeders make their choices for really frivolous reasons; and it IS true that there are the occasional fluff brains and kewpies that breed to the Number 1 dog because he is Number 1, not because he has anything to offer their bitch; or who won't touch a dog unless it has some of Old Rip or whatever flavor-of-the-month they are misty-eyed about; but in my experience those types are not average. MOST of the breeders I am acquainted with are doing the best they can, using the tools of inbreeding and linebreeding and outcrossing, to improve on the overall quality of their dogs over time. I also think it is important to look at the big picture, not focus only on your own breeding program to the exclusion of all else, and see what the BREED is in need of, as well as your personal line. I mean, what do you bring to the table that can advance the Staff or enhance the quality of life for the dogs you breed? I think that most breeders actually DO this, whether they realize it or not; but too few get any credit for the hours they spend studying pedigrees. The key? MODERATION in all things...especially moderation. <|;o)



And as always, the foregoing is only my opinion; with that and a dollar or so, you can get a cup of coffee in your favorite restaurant.



Lenna