Popular-Sire Syndrome: Keeping watch over health and quality issues
By Jerold S Bell, DVM, Tufts Cummings School of Veterinary Medicine
[Every effort has been made to ensure accuracy of information. However,
this is not a substitute for prompt veterinary care. This article
originally appeared in the "Healthy Dog" section of the August, 2004
AKC Gazette. Published with permsission online at Sealyhealthguard.org,
Download PDF version
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
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 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 grand-offspring, 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.
All breeding dogs should be health tested for the conditions seen in
the breed. If your breed has enrolled in the AKC Canine Health Foundation/Orthopedic
Foundation for Animals CHIC program (www.caninehealthinfo.org), prospective
breeding dogs and bitches should complete the recommended breed specific
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)