THE PRICE OF POPULARITY:
POPULAR
SIRES AND POPULATION GENETICS
C.A.
Consider the hypothetical case
of Old Blue, Malthound extraordinaire. Blue was
perfect: Sound, healthy and smart. On week days he retrieved malt balls from
dawn to dusk. On weekends he sparkled in malt field and obedience trials as
well as conformation shows, where he baited to--you guessed it--malt balls.
Everybody had a good reason to breed to Blue, so everybody did. His
descendants trotted in his paw-prints on down through their generations. Blue
died full of years and full of honor. But what people
didn't know was that Old Blue, good as he was, carried a few bad genes. They
didn't affect him, nor the vast majority of his immediate
descendants. To complicate the matter further, some of those bad genes were
linked to genes for important Malthound traits.
A few Malthounds with problems started
showing up. They seemed isolated, so everyone assumed it was "just one of
those things." A few declared them "no big deal." Those
individuals usually had affected dogs. All in all, folks carried on as usual.
Time passed. More problem dogs turned up. People made a point not
to mention the problems to others because everyone knows the stud owner always
blames the bitch for the bad tings and takes credit for the good. Stud owners
knew it best to keep quiet so as not to borrow trouble. Overall, nobody did
anything to get to the bottom of the problems, because if they were really
significant, everybody would be talking about it, right?
Years passed. Old Blue had long since moldered
in his grave. By now, everyone was having problems, from big ones like
cataracts, epilepsy or thyroid disease to less specific things like
poor-keepers, lack of mothering ability and short life-span. "Where can I
go to get away from this?" breeders wondered. The answer was nowhere.
People became angry. "The responsible parties should be
punished!" Breeders who felt their programs might be implicated
stonewalled. Some quietly decided to shoot, shovel and shut-up. A few brave
souls stood up and admitted their dogs had a problem and were hounded out of
the breed.
The war raged on, with owners, breeders and rescue workers flinging
accusations at each other. Meanwhile everybody carried on as always. After
another decade or two the entire Malthound breed
collapsed under the weight of its accumulated genetic debris and went extinct.
This drastic little fable is an exaggeration--but not much of one.
Here's similar, though less drastic, example from real life: There once was a
Quarter Horse stallion named Impressive. The name fit. He sired many foals who
also exhibited his desired traits. But when they and their
descendants were bred to each other, those offspring sometimes died.
Impressive had been the carrier of a lethal single-gene recessive trait. No one
knew it was there until they started in-breeding on him. The situation of a
single sire having this kind of drastic genetic effect on a breed became known
as the "Impressive Syndrome."
Many species and breeds of domestic animals, including dogs, have
suffered "Impressive Syndromes" of their own. But cases like that of
Impressive are only the tip of the iceberg. A single-gene recessive becomes
obvious in just a few generations. But what about more
complex traits?
This is not to say that those popular sires we so admire are bad
breeding prospects. Their many excellent traits should be utilized, but even
the best of them has genes for negative traits.
The problem is not the popular sires, but how we use them. For a
century or more, in-breeding has been the name of the game. (For the purposes
of this article, "in-breeding" refers to the breeding of dogs related
to each other and therefore includes line-breeding.) By breeding related
individuals, a breeder increased his odds of producing dogs homozygous for the
traits he wanted. Homozygous individuals are much more likely to produce those
traits in the next generation.
When a male exhibits a number of positive traits and then proves
his ability to produce those traits he may become a popular sire, one that is
used by almost everyone breeding during his lifetime, and maybe beyond, thanks
to frozen semen.
Since the offspring and grand-offspring and so on are good,
breeders start breeding them to each other. If the results continue to be good,
additional back-crosses may be made for generations. Sometimes a sire will be
so heavily used that, decades hence, breeders may not even be aware of how
closely bred their animals are because the dog no longer appears on their
pedigrees.
This is the case in Australian Shepherds. Most show-line Aussies
trace back, repeatedly, to one or both of two full brothers: Wildhagen's Dutchman of Flintridge and
Fieldmaster of Flintridge. These,
products of a program of inbreeding, were quality individuals and top-producing
sires. They are largely responsible for the over-all quality and uniformity we
see in the breed ring today--a uniformity that did not exist before their birth
nearly three decades ago.
Working lines have also seen prominent sires, but performance
traits are far more complex, genetically and because of the significant impact
of environment. They are therefore harder to fix. Performance breeders will
in-breed, but are more likely to stress behavioral
traits and general soundness than pedigree and conformational minutiae. The
best working sires rarely become as ubiquitous as the best show-line sires.
Not every popular sire becomes so because of his ability to produce
quality offspring. Some have won major events or are owned by individuals with
a knack for promotion. Such dogs may prove to be wash-outs once their get is
old enough to evaluate. But a lot of breeders have been using the animal for
the few years it takes to figure that out, the damage may already have been
done.
Use of even the best popular sires, by its very nature, limits the
frequency of some genes in the breed gene pool while simultaneously increasing
the frequency of others. Since sons and grandsons of popular sires tend to
become popular sires the trend continues, resulting in further decrease and
even extinction of some genes while others become homozygous throughout the
breed. Some of these traits will be positive, but not all of them.
The owners of Old Blue, the Malthound in the opening fable, and those who owned his
most immediate descendants had no idea what was happening under their noses.
They were delighted to have superior studs and even more delighted to breed
them to as many good bitches as possible.
Dog breeding and promoting is an expensive proposition. One usually
winds up in the hole. But owning a popular sire can change that. The situation
looks like a winner for everyone--the stud owner finds his financial burden
reduced while breeders far and wide get to partake of his dog's golden genes.
No one breeding dogs wants to produce sick dogs. A small minority
are callous and short-sighted enough to shrug genetic problems off as the price you pay to get winners, but even they do their best to
avoid letting it come to general attention.
We need a total re-thinking of how we utilize stud animals. No
single dog, no matter how superior, should dominate the gene pool of its breed.
Owners of such sires should give serious consideration to limiting how often
that dog is used, annually, through its lifetime and on into the future, if
frozen semen is stored. The stud owner should also look not only at the quality
of the bitches being presented, but their pedigrees. How much will the level of
inbreeding be increased by a particular mating?
The bitch owner also needs to think twice about popular sires. If
you breed to the stud of the moment and everyone else is doing the same, where
will you go when it comes time to make an outcross?
Finally, the attitude toward genetic disease itself has to change.
It must cease being everyone's dirty little secret. It must cease being a brick
with which we bludgeon those with the honesty to admit it happened to them. It
must become a topic of open, reasoned discussion so owner of stud and bitch
alike can make informed breeding decisions. Unless breeders and owners re-think
their long-term goals and how they react to hereditary problems, the situation
will only get worse.
Copyright 1998 C.A. Sharp is editor of the "Double
Helix Network News". This article appeared in Vol. IV, No. 3 (Summer
1998). It may be reprinted providing it is not altered and appropriate credit
is given.
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