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Evangelizing Canine Genetic Diversity
Hellmuth Wachtel
"Excessive elite breeding" combines only the very best, but
also reduces the genetic pool, leading to a rapid exhaustion of the
genetic improvement margin. Appropriately combining first-rate with very
good subjects makes better progress possible, and better conserves the
gene pool. An example of a well-meant but too strict elite breeding regime
is the German Shepherd Dog in Germany, overly shrinking the gene pool of
the world's most popular and successful breed, with the ensuing inevitable
consequences.
There are canine examples of 'bottleneck breeding," e.g. the
German Kromfohrlaender, a "young" postwar breed
originating from just two dogs; and the Cesky Terrier created by Dr. Horak
using three founders. But survival of longtime inbreds most probably
depends on few or no genetic defects in the founders, which seems to be
extremely rare. Besides, the resulting genetic inflexibility is most
undesirable for many reasons.
Here is my "evangelistic" message:
Seven Theses of Canine Genetic Diversity
- Inbreeding including incest, line and back breeding, popular sire
breeding and exaggerated elite breeding are depleting the breeds
genetic heritage, I call them "close breeding methods "
though habitually this term is used for incest matings (an euphemism).
- As these methods increase the genetic defect risk they can be seen
as a kind of animal experiment that should be reserved for scientific
institutions and are only acceptable for an important purpose. They
are not justified by the slightly better chance to produce a champion.
- All breed clubs used to solemnly state that their breed's health was
their first and foremost concern. This lacks credibility as long as
the above cited methods are not strictly banned in their code of
ethics. Dog breeding should not be gambling with canine health. Even a
breed's absolute purity, while rightly being a sacred principle, must
be secondary in a genetic emergency situation.
- Inbreeding was once a valuable tool in shaping today's breeds. As
these have now reached a high degree of homogeneity it has lost its
importance and turned into a fatal and disastrous habit.
- In order to enjoy a life worth of living, dogs have the right to be
provided with an adequate genetic diversity outfit, just as much as to
good care, feeding, and freedom from abusive treatment.
- The very helpful discovery of genetic markers permitting the
identification of carriers of specific genetic diseases should not be
considered a warrant to continue in the old way as they will not cure
the deterioration of the gene pool caused by the above practices.
- Incest matings are an abomination in dog breeding too, not for any
moral reasons but for the disastrous consequences. overwhelming
practical and scientific evidence, close breeding is abusive breeding.
Overwhelming practical and scientific evidence HAS SHOWN THAT close
breeding is abusive breeding, Highly inbred progeny is
"genetically mutilated."
I tentatively would think if all close breeding stopped today, the
hereditary defect rate would immediately shrink by 10 - 20%. What an
enormous relief of suffering, vet expenditures, and emotional distress....
But every mating of relatives that could be dissuaded from may prevent one
or more sick dogs and thus is worth the convincing effort.
More evangelism:
Evangelism means the spreading of a good message. But one of a
breeder's foremost aims is producing a champion, and if he succeeds, to
spread his (the dogs and his own) fame by offering him far and wide as a
stud. If he is lucky, he even may make much money. In order to improve his
chances, he best uses incestuous mating or at least line breeding. And now
geneticists tell him to act against his interests by outcrossing and very
restrictive use of his stud for the benefit of his breed, if under present
show conditions he will ever be able to produce one doing so.
Canine (genetic) diversity attainment would need a total revolution of
the dog and showing fancy hardly conceivable so far. A good example is in
DOG WORLD MAGAZINE where the authors advocate the reopening of stud books
by the AKC, while on page 19 you read "The breeding of closely
related dogs can have fantastic results or it can produce four-legged
tragedies in terms of health and temperament." As in almost anything
written on dog breeding, there is a warning, but never a clear-cut
dissuasion from inbreeding. It always is defined as a powerful tool for
the knowledgeable breeder, so every breeder will like to prove his
knowledgeability and not miss his chances....
So how to convert an apparent "bad message" to a promising
one for the breeding community?
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Dr. Wachtel has gracefully allowed some of his posts from the Canine Genetics
list to be reproduced here.
For those of you who do not know of it the general site is very good also:
http://www.workingdogs.com
From the Canine Genetics List with permission:
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Jacque (another listmember ) wrote:
Please check out this site:
http://www.ukcdogs.com/cfarticles/cf62599-2.html I'd like your comments on
this ..... especially I would like to know if and/or how inbreeding
depression has been avoided.
Dr. Armstrong replied:
With a few possible exceptions that I will deal with in a minute, all members of all populations of all animals carry a genetic load of about
3-5 lethal equivalents (ie. mutations that would kill if homozygous). The trouble lies in the "equivalents". One LE may actually be 10 genes that
reduce your genetic (reproductive) fitness each by 10%. There appears to be a continuous distribution from 100% lethal to < 1% lethal and maybe
100+ genes involved. If we have 35,000 genes, even if there were 350
detrimental genes, that would only be 1%. When a dog (cat, mouse, human)
is bred, the progeny will, on average, get 50% of the father's load and 50%
of the mothers. If two individuals are selected from a fairly large population, few if any of these genes will actually match up, and even if
they do, most cause only a minor loss of fitness and are not noticed.
If we breed close relatives, they are more likely to have the same set of
underachievers", and will therefore be much more likely to become
homozygous for some. The worst may kill very early and thus tend to eliminate themselves, and the other obvious ones would hopefully be noted
by the breeder and not used to continue the line. The most dangerous are those that reduce fitness by 5-10%. Most will not be detected and we may
even be selecting for some that are linked to traits we like. At some point
someone notes that bitches are having whelping problems, litters appear
to be smaller, etc., but the majority will attribute it to contaminants in
the food, pollutants in the water and the like. These other factors may play
a role, but many of them are likely magnified by the reduced fitness of the
individuals.
How do the lab mouse breeders "get away with it" -- by starting many, many
lines and watching most of them die out as they become more inbred. If you
breed enough lines, a few may make it through without any major health problems, but I would be surprised if they were as fit as their wild
counterparts. (They may be healthier due to better care and nutrition, but
I doubt they'd do as well in the wild.)
I think cheetahs are in much the same situation. They made it through some
event 10-20,000 years that wiped out the North American and other populations, and the African population was lucky. Conservation
biologists still worry about their adaptability. It's not that it can't be done.
It's just that no one has the resources to start several 100 inbred lines of
Poodle, Aussie, GSD, or whatever, or wants to put down hundreds if not thousands of sick puppies. The lab mouse has the advantage of a shorter
generation time and less emotional attachment.
In some ways, though, the breeding of purebred dogs is akin to this,
except that the lines are our breeds, most of which are becoming progressively
more inbred. My observation is that most are on the road to extinction, but
most breeders do not even realize they are part of an experiment.
John
Dr. John Armstrong
University of Ottawa
http://www.magma.ca/~merlin
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