Genetics And Breeding Strategies:
Essays For The Dog Breeder
By Dr. Susan Thorpe-Vargas
Reprinted with permission.
And What Of The Future...?
The fancy has traditionally selected dogs for breeding programs based on arbitrary conformation traits, rather than soundness of structure and overall health. In some cases, form no longer follows function. Breeders and clubs tend to focus on a handful of traits--if that many--at the expense of the whole dog. As for genetics, the relatively simple days of Mendel are not even a memory. Simple dominant or simple recessive genes do not cause most of the disease problems we face in purebred dogs--they are usually polygenic with most of the genes still unknown. What we should do revolves around the question of how to pick a potential breeder. DNA testing is expensive and, at this point in time, available for only certain diseases in certain breeds. The canine genome is not yet complete, and even when it is, it will be many years before the combination of genes causing diseases of interest are identified, and then years before tests are widely available for those diseases. These are noble and necessary goals for sure, but how do they factor into your life as a breeder? In truth, they don't. A word of caution is warranted here: do not hold your breath waiting for the magic test that will tell you whether or not to breed your dog. Let's look at practical and achievable solutions. There are two, and they have been right under our noses all the time: maintain genetic diversity and share information with each other. The goal of a breeder is to produce a "better"" dog. What constitutes improvement is at issue here. If you want to improve a breed, you must know the first principle of evolution. Evolution, by definition, is change and diversification over time in a species. However, if there is no genetic variability, there can be no evolution. Genetic variability is the result of naturally occurring mutations and recombination.
Maintaining genetic diversity will help control the expression of genetic disease, not eradicate it. We are talking quality of life for the individual dog. Genetic diseases do not skip from dog to dog as viruses do. You do not have to inoculate against genetic disease. All you have to do to keep genetically transmitted disease out of your line is not to breed affected dogs. Simply said but not easily achieved. Within this series of essays, we have explored the mechanisms underlying the disease processes, and yet, even with new and greater understanding, we have yet to find the solution to the problem. What it would take is a series of relatively minor but wide reaching changes in philosophy, policy and practice throughout dogdom--in essence, a paradigm shift.
First, clubs must talk to and educate their members, then achieve a cohesive consensus on breeding strategies that reduce the number of affected dogs. Second, clubs must talk to each other and form a coalition to fund studies that will lead to testing for genetic diseases. Third, the AKC must be convinced or otherwise encouraged to participate in a widespread reform and redefinition of breeding stock. Purebred registries should not be scrapped - there is too much history and tradition supported by a huge pyramid base of love and devotion to the dogs. What about adding new category: Breeding stock? Each parent club will have to define what is meant by "breeding stock" for their breed. The definition will involve a listing of the major genetic "faults" known in the breed. One could classify genetic faults by their severity:
Class I - Severe traits would include painful or disfiguring disorders that maim or otherwise cause the animal to be non-functional. Naturally, lethal traits or faults that require medical intervention or treatment for the duration of the animals life would be included in this category. Some few examples of this class: glaucoma, craniomandibular osteopathy, hip dysplasia, entropion, portal systemic shunts, cataracts, retinal dysplasia and detachment, PRA, deafness, dwarfism, inherited kidney disease, diabetes mellitus, hypothyroidism, epilepsy, copper toxicosis, ventricular septal defects, elbow dysplasia, and distichiasis.
Class II - This class would include genetic faults that are easily treated and respond well to therapy, those faults that are corrected by one-time surgery that could be considered primarily cosmetic, and those disorders that make the dog unsuitable for the purpose for which it was bred. Examples of this class would include bite misalignments, hernias, unilateral cryptorchidism, faulty dentition and gait abnormalities. Dogs accepted into the Breeding Stock Register of each club would have to be veterinarian-certified free of Class I or II faults.14
Examination and testing, consistent with current technology would be required as necessary to screen for the diseases recognized in the breed. A number of safeguards would have to be employed to ensure the purity of the Breeding Register. Absolute identification of the animal to include DNA identification, supported by a tattoo and/or microchip would be required. We are dealing with the breed's future, so no bogus registrations can be allowed. [Devil's Advocate time: What about late-onset problems for which there is no screening test? What about problems, like epilepsy, for which there is no positive testing process even for the afflicted?]
It is easier to get information from dissatisfied buyers about what they bought than it is to get information from breeders protecting their standing in the fancy. If breed clubs and AKC were to cooperate, any person registering a puppy, would receive along with the registration from the AKC, a postage-paid card to an open registry. If the puppy develops a genetically transmitted disease, this card would be completed by a veterinarian and forwarded to the registry.
Breeders might try to hide this information, much as they do radiographs of dysplastic dogs they do not send to OFA and PennHip. On the other hand, puppy buyers, who feel they spent good money for a product lacking in quality, would be more likely to comply. It would take only one of the puppy buyers from a litter with an affected puppy to file a report for the process to work.
The registries, if there were more than one cooperating with the AKC, would make their information easily accessible. They could be independent of the AKC or under contract or even be a division of the AKC. The important point is that the probability would be high that should a genetic problem show up in a litter, that litter and the pedigree supporting it would be flagged. Most puppies sold by breeders do not go to show homes and other breeders where this information could be carefully hidden. While the process might not be one hundred percent in 1 generation, over 5 or 10 generations, with a little computer-aided backtracking and cross-referencing, almost every litter with carriers or affected puppies could be identified. The nice thing about genetic disease is that if you know which litters had an affected puppy, you know which dogs to test. It is much easier and more economical to seek out, test and eliminate carriers if you know one of their littermates was affected.
The more conscientious and ethical breeders would also inform the puppy buyers and encourage them to report back any genetic faults encountered during the life of the puppy or in any of its get. As breeders, we leave a standing challenge to parent breed clubs, the AKC and the various registries to do something meaningful about the genetic problems plaguing the purebred fancy. We are not talking about lip service - we are talking about enlightenment, cooperation and action. Over the several decades that hip x-rays have been done, the incidence rate of hip dysplasia in the general dog population has been virtually unaffected. OFA and PennHip, both closed registries, have had minimal impact; and CERF probably less because most dog people do not have their dog's eyes examined every year. What we need are open registries with on-line searchable databases cross-referencing diseases to pedigrees.
One breeder at a time
It should be noted that people, even including scientists, are not always prone to rational facts. This especially applies to dog breeders. New and better information generally gets absorbed slowly. In the case of diversity, we need to struggle with long held beliefs that are no longer viable. Compounding the problem, in the case of inbreeding, these outmoded practices produce conformation ring success, but at what untold cost? Those of us who preach diversity find it very discouraging because these "old dogs" do not want to learn new tricks. If one hangs about the breed ring long enough, the prospect of educating breeders becomes overwhelming. However, instead of lamenting each incident and outcome of the old ingrained inbreeding paradigm we need to take one step at a time and rejoice in any and all progress. There is hope. It may be a human generation--and seven dog generation--away! But hope, nonetheless. You read this book, didn't you?