Responsible dog breeders have long worked toward breeding healthier dogs.  Following the establishment of the Orthopedic Foundation for Animals in 1966, screening for physical evidence of genetically based disease became the norm.  During the latter part of the twentieth century, it was commonplace for an otherwise acceptable dog to be eliminated as a breeding prospect due to a “failed” health screening.  Advances in scientific technology coupled with the completion of the canine genome project have resulted in a veritable explosion of genetic tests available to breeders.  At the same time as our ability to screen and test for genetic disease is increasing at a geometric rate, our gene pools are suffering from smaller actual numbers of dogs and increasing genetic homogeneity of available breeding candidates.  This situation requires a paradigm adjustment on the part of all responsible breeders.  If we continue to “test and eliminate” dogs, we will soon find ourselves with nothing left to breed.  We need to develop a more useful way of managing test results, as well as pedigree-related health information, so that we can more effectively manage serious disease processes in our breeds.

First we must recognize the usefulness of continuing various types of genetic testing.  Test results give us information that we did not have before.  We can use test results to improve mate selection for our dogs.  All dogs carry genes for deleterious conditions, whether or not we actually see them expressed.  The more information that we have available to include in the decision making process, the more steps that we can take to move our breed toward long term health.  We know that more genetic diversity within a given breed not only facilitates the overall health and well-being of the individual animals, but it gives us more flexibility when confronted with the need to drastically reduce the incidence of a particularly devastating problem.

Canine geneticists encourage us to use a wider variety of dogs in our breeding programs than was previously considered optimal.  One of the simplest ways to increase genetic diversity is to avoid the popular sire syndrome.  In his article entitled, Popular-Sire Syndrome: Keeping watch over health and quality issues in purebreds, Jerold S Bell, DVM, Tufts Cummings School of Veterinary Medicine says, “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.”

In his article, Population Genetics in Practice: Principles for the Breeder, J. Jeffrey Bragg not only warns against the popular sire syndrome, but advocates for an equal number of males and females to be used in breeding programs.  He says, “Breeders should make a great effort to maintain a reasonably equal numerical balance of sires and dams; it is unwise consistently to use fewer individual sires than dams. The so-called “popular sires” syndrome, in which a small number of elite show or trial winners sire grossly disproportionate numbers of progeny in a breed population, has received much discussion and attention. What may not be so well realised is that this selfsame syndrome is repeated in miniature in most kennels, where one or two of the “best” males cover all the bitches, sire all the litters. (How often has one heard it put forth, and not only by novices, that “the best males should sire all the litters!”) Any significant imbalance between the number of sires and dams automatically restricts the effective breeding population. In order to avoid such needless reduction, just as many individual males as bitches should contribute to the population; this holds true whether we speak of the breed population as a whole, or of the population within a single kennel.”

Another concept presented by Bragg is the idea that multiple pups from any quality litter should be bred.  As purebred dog breeders, we have been encouraged since the pet population explosion of the 1970’s and 80’s, to keep the best (presumably show quality) pup and place the balance of the litter on spay/neuter contracts in pet homes.  While that may have been both appropriate and useful at the time, our current situation involving shrinking numbers and plummeting diversity call for a different strategy.  Bragg says, “The breeder should strive to ensure that at least two of every litter (unless it should happen to be one of those litters that really had best be forgotten) contribute to the next generation; half the litter should be the ideal, though perhaps a difficult one to maintain. In every instance in which only one progeny from a given mating contributes to the next generation, automatically and infallibly half of the available genetic diversity in that line is lost permanently! If two progeny contribute the theoretical average loss is reduced to 25%, still less if more littermates contribute. This single point is a major source of losses of genetic diversity among purebreds, yet it often goes totally unconsidered by the breeder.”  It is not hard to imagine that dogs might contribute to the next generation because they are beautiful show dogs, excellent herding or hunting dogs, motivated SAR dogs or any combination of these and other areas of instinctive talent.

The crucial attitude adjustment involves making breeding decisions that accomplish two things.  First, individual dogs (and their close relatives) that are affected, carriers or have a high-risk pedigree analysis for genetic conditions should not necessarily be eliminated from reproducing as long as a suitable mate can be found without excessive risk for that particular disease.  This is certainly more difficult to accomplish in the case of polygenic and multifactorial diseases like epilepsy and hip dysplasia, than it is in more straight forward conditions like PRA.  None the less, a breeder who is willing to pursue all the possible sources of information and integrating that into a useful strategy for reducing the incidence of serious conditions in their breeding program can meet with considerable success.  Additionally, subscribing to the overall goal of increasing the level of heterogeneity in their own breeding program will provide significant benefits related to overall health and well-being.  Breeders need to work together to enjoy the maximum benefits of reducing the incidence of serious health conditions in our breeds and to manage our gene pool to effectively maintain genetic diversity in the long term.

© Peri Norman 2016