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by Eddie Dziuk, originally published by and reprinted with permission
of Dog News
The decision to breed dogs brings with it a host of responsibilities. Responsible dog breeders properly house, feed, and care for their dogs. They provide proper socialization for their puppies, and go to great lengths to screen perspective buyers, and place their puppies in good homes. Responsible dog breeders do not allow their dogs to end up in rescue organizations, they maintain a lifelong commitment to the animal. The list goes on, these are but a few of the responsibilities that separate the serious, responsible dog breeder from "backyard" breeders and commercial operations.
Another area of responsibility assumed by the dedicated breeder is a commitment to health issues. This commitment to overall canine health goes beyond providing puppies with their first shots. It goes beyond a concern of keeping the puppy well until the warranty after the sale has expired. While no one, commercial breeders included, wants to produce puppies that are deaf, go blind, seize, or are lame, the actions taken up front to minimize inherited diseases help define what makes a person a serious, dedicated, and responsible breeder.
Conformation traits, working ability, and temperament are routinely factored into the selection criteria leading to a particular breeding. Health concerns need to play a similar role in these decisions. The prioritization and balance of these selection criteria contribute to making dog breeding an art, not a science. However, even as an art form, there is a scientific component. Often, the most successful breeders are those who have been working with a long line of particular dogs. They have personal knowledge of generations of dogs within the pedigree. They have experienced first hand the dominant traits, both positive and negative, which certain dogs carry. In short, they have data; information, which allows them to make more informed breeding decisions.
The role of canine health databases is to apply the same concept of knowledge to health related issues. They capture health information on individual animals and allow breeders to make more informed breeding decisions by including health concerns in their mix of selection criteria.
In recent years, a number of DNA tests for specific diseases have been developed. These tests remain the "gold standard" since actual genotypic information is derived. Test results, their submission into a health database, and the applied use of the database can have significant results in reducing the prevalence of a disease. PRA in Irish Setters is an outstanding example. For years the Irish Setter Genetic Registry maintained statistics on test matings in order to identify carriers of the disease and eliminate them from the breeding pool. Their data assisted researchers in identifying the actual disease causing mutation and ultimately led to the development of a DNA test for PRA in the breed. As a result, testing along with applied use of the database has greatly improved the health of the breed.
Unfortunately, most inherited traits, including inherited diseases, are probably polygenic. They have a complex mode of inheritance influenced by multiple gene pairs. To date, no DNA tests have been developed to identify the specific combination of mutant genes responsible for any polygenic disorders. Therefore, decisions regarding a dog's suitability for breeding purposes rely on phenotypic evaluations. The complexity of polygenic traits results in a wide range of expression, from least to most desirable. It is the reason why two dogs of ideal conformation may produce offspring less than ideal, and the reason why the mating of two dogs that are phenotypically normal for a disease may produce affected offspring.
When dealing with genetic unknowns, it is difficult to control the incidence of a polygenic disease. Phenotypic evaluations allow us to make assumptions on the dog's genetic makeup. However, too often, breeding decisions are based purely on the potential sire and dam's traits. Although progress towards a desired outcome can be achieved in this method, it will almost certainly be slow and result in surprises along the way. This is where health databases can play a significant role. As the database is populated, incorporating information not only on the parent's phenotype into the breeding decision, but phenotypic information from close relatives such as siblings, half siblings, aunts, uncles, grand-sires, and grand-dams becomes possible. This allows breeders to make a more accurate assumption regarding the potential sire and dam's genotype, and allows them to apply greater selective pressure to produce desired and avoid undesirable traits.
At the heart of the OFA's quest to assist breeders in lowering the incidence of genetic diseases are the OFA databases. When the OFA was formed in 1966, one of its main objectives was to "advise, encourage, and establish control programs to lower the incidence of orthopedic and genetic diseases". This objective remains firmly in place today. The databases of the OFA give breeders access to the health screening results of hundreds of thousands of dogs, allowing them to increase the selective pressure to produce healthy dogs free of inherited diseases.
The OFA's original interest was hip dysplasia. This continues to be a major focus of the organization today. However, in recent years, scientific advances and the enhanced ability to diagnose heritable diseases have led to the development of several additional databases. These include databases for elbow dysplasia, congenital cardiac disease, autoimmune thyroiditis, patellar luxation, a number of databases based on breed specific DNA tests, and the most recent additions, legg-calve-perthes (LCP) and sebaceous adenitis (SA).
The hip dysplasia, elbow dysplasia, and legg-calve-perthes databases are based on radiographic evaluations. Since radiographic interpretation and application of diagnostic criteria can differ among veterinarians, the OFA offers a solution by providing experienced, consistently applied, specialist interpretation. The OFA maintains a pool of approximately twenty-five independent, consulting radiologists. Each is a board-certified Diplomate of the American College of Veterinary Radiology. For hips and elbows, three randomly selected radiologists from the pool evaluate each radiograph. Hip joint conformation is assigned one of seven phenotypes: Excellent, Good, Fair, Borderline, Mild, Moderate, and Severe. Elbow conformation is graded as Normal, or Grade I, II, or III Dysplasia. The final OFA grade is based on a consensus of the three independent opinions.
The remaining OFA databases differ in that the actual evaluation is performed by a source outside the OFA. For the patellar luxation and congenital cardiac databases, an attending veterinarian performs the evaluation. The veterinarian must have the advanced training necessary to perform an accurate diagnosis, and the OFA highly recommends that board certified specialists perform these examinations. For the thyroid database, the evaluation is based on laboratory assay performed at one of seven approved OFA labs. The SA database is based on skin punch biopsies evaluated by approved dermapathologists. And finally, the DNA databases are based on results from specific laboratories licensed to perform the tests. The OFA's function with these soft tissue databases is to develop consistent diagnostic test protocols with veterinary experts, and offer breeders the databases in which to register the test results.
The common thread among all the databases remains the OFA's original objective to establish control programs to lower the incidence of genetic diseases. However, to be a useful tool, breeders and owners must acknowledge the value of such databases, and embrace the submission of data. With over 800,000 studies on file, the OFA has the world's largest data bank on canine hip evaluations. Most breeders who contribute to the data and use the database in their selection criteria have seen improvements in the health of their dogs. Although some information is better than none, for the newer databases breeders and owners must remember that it may take years for the database to become populated with enough information to allow the type of in depth pedigree research that is the goal of the databases.
The last few years have seen a great deal of focus and criticism on the practices of commercial breeders. Within the fancy we are quick to differentiate ourselves, calling ourselves responsible breeders striving to preserve and improve the breed. However, the term responsible breeder is one that is earned, not assigned based on number of litters bred, or mere participation in AKC events. Complacency over health issues, especially when in pursuit of the blue ribbon, equates to irresponsibility. As responsible breeders, we must recognize health issues where they exist, educate ourselves on the issues, and incorporate health issues into our breeding selection criteria with a specific goal of reducing inherited disease. In addition to the OFA, canine health databases are maintained by CERF, PennHIP, parent clubs, and by several leading research institutions and universities. All breeders are urged to breed responsibly and use these tools for the improved genetic health of our purebred dogs.