Popular-Sire Syndrome: Keeping watch over health and quality issues in
purebreds
By Jerold S Bell, DVM, Tufts Cummings School of Veterinary Medicine
(This article originally appeared in the “Healthy Dog” section of the
August, 2004 AKC Gazette)
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An important issue in dog breeding is the popular-sire syndrome.
This occurs when a stud dog is used extensively for breeding,
spreading his genes quickly throughout the gene pool. There are two
problems caused by the popular-sire syndrome. One is that any
detrimental genes which the sire carries will significantly increase
in frequency – possibly establishing new breed-related genetic
disorders. Second, as there are only a certain number of bitches
bred each year, overuse of a popular sire excludes the use of other
quality males, thus narrowing the diversity of the gene pool.
The popular-sire syndrome is not limited to breeds with small
populations. Some of the most populous breeds have had problems with
this syndrome. Compounding this, there are several instances where a
popular sire is replaced with a son, and even later a grandson. This
creates a genetic bottleneck in the breeding population, narrowing
the variety of genes available.
Every breed has its prominent dogs in the genetic background of the
breed. But most of these dogs become influential based on several
significant offspring that spread different combinations of the
dog’s genes over several generations. The desirable and undesirable
characteristics of the dog were passed on, expressed, evaluated by
breeders, and determined if they were worthy of continuing in future
generations.
The problem with the popularsire syndrome is that the dog’s
genes are spread widely and quickly - without evaluation of the
long-term effects of his genetic contribution.
The Challenges
The problem with the popular-sire syndrome is that the dog’s genes
are spread widely and quickly - without evaluation of the long-term
effects of his genetic contribution. By the time the dog’s genetic
attributes can be evaluated through offspring and grandoffspring,
his genes have already been distributed widely, and his effect on
the gene pool may not be easily changed.
In almost all instances, popular sires are show dogs. They obviously
have phenotypic qualities that are desirable, and as everyone sees
these winning dogs, they are considered desirable mates for
breeding. What breeders and especially stud-dog owners must consider
is the effect of their mating selection on the gene pool. At what
point does the cumulative genetic contribution of a stud dog
outweigh its positive attributes? A popular sire may only produce a
small proportion of the total number of litters registered. However,
if the litters are all out of top-quality, winning bitches, then his
influence and the loss of influence of other quality males may have
a significant narrowing effect on the gene pool.
In some European countries, dog-breeding legislation is being
considered that limits the lifetime number of litters a dog can sire
or produce. If, however, certain matings produce only pet-quality
dogs, but no quality breeding prospects, should the dog be
restricted from siring a litter from a different line? The popular
sire’s effect on the gene pool is on the number of offspring that
are used for breeding in the next generation, and how extensively
they are being used. This cannot be legislated.
At what point does a stud-dog owner determine that their dog has
been bred enough? It can be difficult to deny stud service when
asked, but the genetic effect of a dog on the whole breed must be
considered. If everyone is breeding to a certain stud dog, the
intelligent decision may be to wait and see what is produced from
these matings. If you still desire what the stud dog produces, it is
possible that you can find an offspring who has those positive
attributes, and also a genetic contribution from its dam that you
may find desirable. If a popular stud dog deserves to make a
significant genetic contribution to the breed, doing so through
multiple offspring, and therefore getting a mixed compliment of his
genes, is better than focusing on a single offspring.
Wait-and-See Approach
All breeding dogs should be health tested for the conditions seen in
the breed. If your breed has enrolled in the AKCCanine Health
Foundation/Orthopedic Foundation for Animals CHIC program (www.caninehealthinfo.org),
prospective breeding dogs and bitches should complete the
recommended breedspecific health testing prior to breeding. These
may include hip radiographs, CERF eye examinations, or specific
genetic tests.
It is important to monitor the positive and negative characteristics
being produced by popular sires. While it is satisfying to own a
popular stud dog, a true measure of a breeder’s dedication is how
negative health information in the offspring is made available. All
dogs carry some undesirable traits. Based on the variety of pedigree
background of bitches who are usually brought to popular sires,
there is a greater chance that some undesirable traits could be
expressed in the offspring. It is up to the stud-dog owner to keep
in touch with bitch owners, and check on the characteristics that
are being produced.
Some breeders will argue that the strength of a breed is in its
bitches, but the fact remains that the stud dogs potentially have
the greatest cumulative influence on the gene pool. There will
always be popular sires, and that is not necessarily bad for a
breed. But a dog’s influence on a breed should be gradual, and based
on proven production and health testing. Maintaining surveillance of
health and quality issues in breeding dogs and their offspring, and
preserving the genetic diversity of the gene pool, should allow a
sound future for purebred dogs.
(This article can be reproduced with the permission of the author.
Jerold.Bell@tufts.edu)
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