Genetics And Breeding Strategies:
Essays For The Dog Breeder
By Dr. Susan Thorpe-Vargas
Reprinted with permission.
The Shallow End of the Gene Pool
The ability to go back to stock from a breed's country of origin (COO) in order to expand the gene pool is a process known as introgression. The basic tenants of the AKC make such a process difficult to impossible for dogs originating in most "non-western" societies unless special exceptions are made. Many COO dogs come from countries in which registries do not exist or do not meet the AKC's specific standards. In the early development of many breeds, the AKC often facilitated expansion of the gene pool. Most recent attempts to introduce new genetic material by the registration of COO stock have met with the AKC's steadfast position that unregistered stock cannot be directly integrated into the studbook. The AKC will sometimes make exceptions in the face of compelling health or medical reasons. In such cases the parent breed club must vote in favor of such a step and then petition the AKC to open the studbook for a brief time. The Saluki, for example, is an ancient breed that still exists throughout its native Middle East. Its Bedouin owners can recite its pedigree for generations, but such is not acceptable proof of purity for the purposes of AKC registration. The AKC Saluki is derived in most part from a small number of founding dogs brought to England around the 1920s. In 1945, two Salukis bred by King Ibn Saud came to this country and after some persuasion, the AKC made a special ruling whereby descendants removed by three generations from these imports could be registered, as long as the generations in between were always bred to registered stock. Today, imported COO Salukis are formidable competitors in coursing trials. Attempts to gain AKC recognition for these dogs, however, have been unsuccessful, largely because of a lack of consensus by the parent club as well as the lack of any overwhelming genetic problems that would lend urgency to the matter.
In the cross fire
In some breeds, no COO stock exists, or that which does exist shares the same problems as the AKC stock. In such cases, crosses to other breeds may be the only way to introduce new genes. Early in the creation of breeds, such crosses were commonplace. For example, although the Shih Tzu is an ancient breed, at the beginning of this century the breed is thought to have become extinct in China. Modern Shih Tzu descend from seven dogs and seven bitches, one of which was not a Shih Tzu, but a Pekingese. This cross occurred in 1952, long before AKC recognition of the breed. While the early registration bodies sometimes sanctioned crosses to other breeds, after a breed was established, they allowed crosses only in the rarest of circumstances.
The Dalmatian is a breed with a genetic predisposition for abnormal uric acid metabolism that leads to painful and debilitating stone formation. In 1988, at the behest of the board of directors of the Dalmatian parent club, and with the approval of the AKC, a cross was made to a Pointer in an attempt to introduce the genes for normal uric acid metabolism into the Dalmatian genome. The plan was to breed the normal progeny of this initial cross back to Dalmatians, continuing for many generations until their descendents were essentially Dalmatians with no trace of Pointer (except for the normal uric acid metabolism). With each backcross (crossing the mixed progeny back to pure Dalmatians,) the proportion of Pointer chromosomes would decrease by one half. This is a common plan for the introduction of a new gene into another population, although several factors can slow or halt its progress. These factors include linkage wherein the trait being selected for is on the same chromosome as other traits that may be essential for type. If, for example, the trait for normal uric acid metabolism was on the same chromosome as the trait for patches, acceptable in Pointers but not in Dals, a decision for health would also be a decision against type. Even so, in time, the Pointer derived chromosome bearing the introduced allele will cross over and exchange genetic material with its homologous Dalmatian derived chromosome and hopefully breed true for the Dalmatian type without the metabolic defect.
This did not happen, though. The descendants with normal uric acid metabolism tended to have ticking, instead of spotting, suggesting the possibility of either linkage or pleiotropic effects. Rember that pleiotropic effects are those where one gene causes several diverse effects. Further problems arose with a change in consensus about the project within the Dalmatian Club of America. The club subsequently objected to the registration of the crossbred progeny and lifted the registration privileges for these dogs. Thus, although the experiment was a medical success, it was not successful from the viewpoint of maintaining Dalmatian type or achieving widespread acceptance. The important lesson in this case, however, is not that the venture failed, but that the AKC had the foresight to approve it in the first place. Perhaps the most important lesson was one of requiring full consensus of all parent club members before undertaking a project of this nature--"full consensus" implies unanimous, which is impossible in most clubs. The AKC now requires a full membership vote from the parent club before granting approval.
One of the rarest breeds in America is the Wirehaired Pointing Griffon. In the 1980's, the breed's limited gene pool resulted in the decision by some breeders to cross the breed with the Cesky Fousek, a European breed. Griffon breeders did not universally approve the project and the AKC did not grant recognition to the resultant dogs. Breeders have the liberty of choosing the direction of their own breeding programs. If they choose to cross their dogs to another breed without a priori parent club and AKC approval, they cannot expect AKC recognition of their stock--no matter how good their intentions.
While it is clear that in some cases the AKC will consider "breaking the rules" in order to promote genetic health and diversity, no set guidelines seem to exist by which a parent club can petition for such an exception. Shouldn't a published set of criteria be available so that breed clubs know at what point they may reasonably resort to this step? Should the breed club or the AKC be the final authority when deciding if such exceptions are to be made?
It is the parent breed clubs that initially develop breed standards, maintain stud books, and petition AKC for recognition of the breed and the club. Even after agreeing upon a standard, the parent club may consider amendments to it and, if deemed appropriate, change it. In developing a standard, a parent club exerts tremendous power over the genetic future of a breed. In some cases, standards require physical characteristics that are inconsistent with hardiness. For example, brachycephalic features predispose a dog to breathing difficulties, diamond shaped eyes to entropion and/or ectropion, excessive wrinkling to moist dermatitis, and excessive size coupled with deep chests to gastric torsion (bloat). In most of these cases, the breed standards were drawn up long before the association of the traits with physical difficulties was known. Such traits have become so ingrained as basic to breed type that breeders and parent clubs choose to retain them despite their associated problems. Since the parent club has sole discretion over the breed standard, only the breed club can effect a change in the standard to change the essence of type and reward healthier, but less traditionally typey, specimens. In almost every case in which type has been at odds with health, parent clubs have chosen to give type precedence. The results are obvious!
Breed standard disqualifying faults also affect the genetic health of a breed. The AKC has several disqualifying faults applicable to all breeds; perhaps the best known of them is unilateral or bilateral cryptorchidism--the failure of one or both of the testicles to descend normally into the scrotum. Since this fault is less detrimental to health than a plethora of other far more serious faults with far greater heritability, the universal disqualification of such dogs is of questionable value to any breed. Several parent clubs impose further disqualifications, usually for traits considered extremely untypical for the breed. Common disqualifying faults are for dogs over or under a certain weight or height, for different eye color, or coat colors or types. Dogs with disqualifying traits cannot be judged at a conformation show, but may compete in other venues. By banning these dogs from conformation competition, parent clubs hope to discourage breeding from them and perpetuating the offensive trait. Removal of dogs from the breeding population based upon arbitrary aesthetics can do more harm than help, especially in cases where the breed has a limited gene pool and the banned trait has no strong hereditary component.
Lack of appreciation of genetic aspects of a trait can result in illogical and detrimental disqualifications. One example is the Mantle (also know in the USA as the "Boston") Great Dane. These dogs are black with typical "Irish marked" coat pattern, that is: white feet, tail tip, muzzle, and collar, just like the typical pattern of the Boston Terrier. This color pattern was, until recently, listed as a disqualifying fault under the AKC standard for the breed. Yet serious breeders of Harlequin Great Danes have routinely used the Mantle in their breeding programs. Breeding a Harlequin to another Harlequin statistically results in 25% Harlequins, 25% merle (disqualified), 25% white (disqualified and commonly defective) and 25% Mantle (until recently also disqualified). This gives a predicted percentage of show marks of no more than 50% (some further losses may occur from unsuitable markings on Harlequins and Mantles). Breeding a Harlequin to a Mantle, however, results on average in 25% Harlequin, 50% Mantle, and 25% merle; with potentially 75% show marks produced in this breeding. Thus, a substantial proportion of dogs produced from the traditional breeding of Harlequin to Harlequin--perfectly acceptable colored parents--will be disqualified from breed competition by virtue of the combination of acceptable genes that together produce an unacceptable color pattern in this breed. Some of these disqualified dogs may be of such high quality otherwise that they are sought after for breeding back to Harlequins.
Before the introduction of the Mantle this was often the case as their use as a breeding partner to a Harlequin, as noted above, actually results in a greater percentage of acceptably colored offspring than would a Harlequin to Harlequin breeding. It also avoids the production of potentially defective homozygous merle dogs, known as white Danes. Unfortunately, because these Mantles were disqualified from competition, their quality, until recently, could not be objectively judged by way of conformation awards or titles. It was obvious to many that the standard with these disqualifications was counterproductive. Finally, in 1996, in recognition of the importance of the Mantle Dane to the breeding of Harlequins, the Great Dane Club of America voted to change the breed standard to accept the Mantle Dane as an acceptable color. Changing the standard is one of the heaviest responsibilities that a parent club can undertake, and to do so in recognition of genetic mechanisms is a progressive step for a parent club. Unfortunately, not all clubs have shown such an ability to accept genetics over tradition.
In other breeds, disqualifications have been implemented in recognition of health problems related to certain traits. In 1979, a "white" Doberman Pinscher named Sheba was AKC registered. She was undeniably eye-catching, with a light cream coat, translucent blue eyes, and pink nose and eye rims. Her offspring were crossed to each and produced more such dogs. These striking animals aroused much interest, but were apparently tyrosinase positive albinos. Not only were these dogs considered untypical for the breed, but because albinism can be associated with health problems, especially those from ultraviolet exposure, the Doberman Pinscher Club of America acted not only to disqualify these dogs, but worked with the AKC to develop a scheme whereby dogs possibly carrying the gene for albinism could be identified by their registration numbers. Such dogs are identified with a "Z" as part of the litter or individual registration, the Club having acted proactively to limit this problem - a very postive move.
In recent years, most parent clubs have formed breed health committees, the success of which depends upon many factors. Some clubs have a large membership from which to draw and an open door policy which has brought in a diversity of educated and dedicated committee members. But some clubs still operate under closed memberships, in which prospective members must be sponsored by existing members and voted upon by the full membership. These clubs have been less apt to deal with health issues while preferring to preserve the status quo. Political issues, of course, are rampant within any breed, and control of the parent club means control of the breed standard--and ultimately the future of the breed. Thus, in certain breed clubs, because of either small breed numbers or exclusionary practices, the chance of forming a strong health committee is considerably lower than in those clubs with a more diverse membership.
The first step a breed health committee faces is identification of health problems. This step is not as simple as it may seem. Breeders may have a "feeling" about what may be a problem based upon personal experience and anecdotal reports. The problem then becomes one of determining whether these problems are breed specific or common to all breeds. For example, if a breeder knows of ten dogs over the past three years that suddenly fell over dead at a young age, this might raise some suspicion that the breed had a problem. But perhaps this is no more than would be seen in any breed of dog. The problem is that 95% of that breeder's contacts also have the same breed of dog; it would be very unlikely that the breeder would ever hear about the same circumstance in another breed simply because of lack of communication. Thus, a major problem in breed specific health surveys is one of bias.
While it is unrealistic to expect parent clubs to have the expertise conduct statistically sound and unbiased health surveys, they are being forced to shoulder this responsibility. Some have done a better job of tackling it than others. The greatest barrier to parent club health surveys is lack of trust on the part of breeders, since those collecting the information are often that breeder's competitors. Though hiding health information may seem petty and dishonest, recall that many breeders have a lifetime of hard work, study, money, and emotion invested in their line of dogs. They fear that if they are the only ones to come forward with information, they may be the only ones branded as having unhealthy dogs, effectively terminating the line to which they have devoted their lives. In popular breeds much of the information thus comes from individual pet owners. In some other breeds efforts are undertaken to ensure anonymity.
For example, the Salukis In Good Health Committee developed a process in which identifying information and medical information pertaining to a dog are sent in separate sealed envelopes, coded by a "middle-man", and sent on to separate data entry people so that no person ever sees the medical and identifying information together. Only in the final step are the two sets of information associated within a third database that encrypts the information so that actual identification of animals is still inaccessible to committee members. It is this information that is ultimately used for performing analyses.
Code of ethics
Most parent breed clubs maintain a standing ethics committee to develop, maintain and enforce some form of code of ethics. Such codes are known by various names such as Guidelines for Responsible Ownership, Guidelines for Breeders, Guidelines for Ethical Conduct, Ethical Guidelines, Mandatory Practices, Principles of Integrity, Statement of Conduct, Canon of Ethics, Breeders Code and Code of Recommended Practices. There are several more variations upon this theme, but in general, the parent clubs' codes of ethics make vague and not very binding statements about genetic health, ranging from no mention at all, to actually listing the diseases of interest and the screening required.
Some parent clubs have had serious internal political problems when establishing a standing ethics committee, with the result being that some clubs have yet to progress this far. Other clubs have official committees, but they are kept out of sight and out of mind. In some clubs, because of the personalities and beliefs of some of the more successful members, those individuals have severely controlled or thwarted the actions of such committees. When one of the more successful breeders with more champions bred and shown refuses to screen for hip dysplasia, the club is often powerless to enforce screening requirements. In such cases, genetic screening becomes "recommended," "encouraged" or "should be considered."
There are several breed clubs that do in fact list the screening that should be done and say that such screening is mandatory under the code of ethics. A number of codes of ethics mention the Orthopedic Foundation for Animals (OFA), but no other registry such as the Canine Eye Registration Foundation (CERF). This is a step in the right direction, but one finds virtually no evidence that anything has been done to discipline or terminate membership of any successful breeder who fails to follow the club's screening regimen. In fairness to breed clubs, it is difficult in a litigious society to attempt to force any sort of genetic testing without that attempt resulting in internal lawsuits. If changing a breed standard to add a comma to correct punctuation is difficult, think of how difficult it might be to establish a genetics committee to interface with an ethics committee and develop a genetic screening regimen appropriate to the breed. Imagine the legal tests when a successful breeder is censored by some means for not conducting such screening.
The answer lies in educating the club membership. Advertisements of top dogs need to include the genetic screening supporting them. Articles need to be frequently published in the club and breed magazines/newsletters questioning the folly of purchasing a dog from anyone that did not have an effective genetic screening regimen. In our democracy, the free market exerts the force for change that is otherwise prevented by the costs of litigation. The puppy buying public is slowly becoming aware of the problems of genetically inferior dogs. States are rushing to enact puppy lemon laws.
To some, the AKC is becoming known as the registry of sick dogs. Any breed club's attempt to rise above the mire will serve to differentiate that breed from the "You don't want one of those, they have a lot of health problems." Individual breeders can enhance the desirability of their puppies by documenting generations of genetically healthy dogs.
Sample codes of ethics
Following are representative extracts from a sample of various breed clubs codes of ethics:
Akita "I will keep well informed in the field of genetics and work to eliminate hereditary defects from the breed... I will participate in a program of hip x-raying and eye examinations by qualified veterinarians to eliminate hip dysplasia and congenital eye problems. When an Akita has hereditary faults of such nature as to make his or her use for breeding detrimental to the furtherance of the breed, that dog shall be neutered/spayed."
Basenji "Ethical breeders should discuss openly and honestly the genetic and physical problems that have occurred in their lines. This should include the potential of these problems to be passed on, especially in cases where testing can indicate only that a dog is currently free of a problem, but cannot determine that the problem or the ability to pass it on will not be inherited. Stud dogs or brood bitches who produce offspring of consistently poor quality or with genetic problems known to be inherited in the breed are therefore of no value as breeding stock and should not be used again."
Basset Hounds "Breedings will be directed toward producing Basset Hounds of exceptional quality in breed temperament, Basset Hound type and ability to hunt game. Only healthy and mature dogs and bitches free of congenital defects and of characteristic breed type, sound structure and temperament shall be bred."
Borzoi "No animal selected for breeding should have any serious hereditary defects as determined visually and by veterinary examination."
Chesapeake Bay Retriever "Be aware of genetic defects which can be harmful to the breed. When breeding, endeavor to select animals that will reduce the incidence of genetic problems while enhancing the positive attributes and abilities of the breed. Be open with all persons interested in the welfare of the Chesapeake Bay Retriever and discuss possible physical or temperament defects in your own stock."
Dachshund no statement concerning genetic fitness for breeding.
Doberman Pinscher "Stud dogs should not be bred prior to one (1) year of age and should be in good health and free from communicable diseases and disqualifying faults." ... Any bitch accepted for stud service should be at least 18 months of age, in good health and free from communicable diseases and disqualifying faults."
English Cocker Spaniels no standing ethics committee. Statement of Conduct is silent on genetic health.
Field Spaniels "Breed only healthy and mature animals who are free from serious congenital and hereditary defects."
Golden Retrievers "Owners of breeding animals shall provide appropriate documentation to all concerned regarding the health of dogs involved in a breeding or sale, including reports of examinations such as those applying to hips and eyes. If any such examinations have not been performed on a dog, this should be stated."
"Animals selected for breeding should:
(i) be of temperament typical of the Golden Retriever breed; stable, friendly, trainable, and willing to work. Temperament is of utmost importance to the breed and must never be neglected;
(ii) be in good health, including freedom from communicable disease;
(iii) possess the following examination reports in order to verify status concerning possible hip dysplasia, hereditary eye or cardiovascular disease.
Hips: appropriate report from Orthopedic Foundation for Animals; PennHip; Ontario Veterinary College; BVA/KC Hip Score (Great Britain) or at least a written report from a board-certified veterinary radiologist (Diplomat of the American College of Veterinary Radiologists).
Eyes: appropriate report from a Diplomat of the American College of Veterinary Ophthalmology (ACVO), or from a BVA/KC approved ophthalmologist (Great Britain).
Hearts: appropriate report from a Diplomat of the American College of Veterinary Medicine, Cardiology Specialty.
Consideration should be given also to other disorders that may have a genetic component, including, but not limited to epilepsy, hypothyroidism, skin disorders (allergies), and orthopedic disorders such as elbow dysplasia and steochondritis."
German Shepherd Dog no statement of genetic health in the Breeders' Guide.
German Wirehaired Pointer "Only those dogs free of recognized genetic defects shall be used in a breeding program."
Italian Greyhound "It is not always possible to prevent the occurrence of inherited diseases, as there are not yet definitive tests to identify carriers of genetic diseases. A breeder's obligation with regard to genetic diseases is to make every effort to prevent their occurrence and to share openly and honestly all information available regarding the genetic health status of his/her dogs. While elimination of genetic diseases is a worthy goal, the converse is that excessive culling of animals from the gene pool may have the equally deleterious effect of limiting the gene pool in the breed. Breeders should be cautious about removing animals from the breeding pool solely because they are distantly related to an affected individual."
Irish Setter "Make every effort to learn about the structure, anatomy, action, behavior and other inheritable traits of the Irish Setter. To use this information to adhere to the breed standard and produce sound, healthy dogs with good temperament... To use or give service only to registered stock that is believed to be free of serious abnormalities which are considered inheritable... When selling an Irish Setter known to manifest hereditary defects considered to be detrimental to the breed, use written contracts or spay/neuter agreements to prevent the dog from being bred."
Miniature Pinscher "Breed only mature animals in good health, free from communicable diseases and major genetic faults."
Pekingese no mention of genetic health in Code of Ethics.
Pointer "Only animals of quality with characteristic type, sound structure and temperament, and free of congenital faults should be bred."
Pugs no mention of genetic health in Code of Ethics.
Rhodesian Ridgebacks "Only dogs screened and certified clear of hip dysplasia shall be bred. Breeders are encouraged to screen for all appropriate hereditary disorders."
Rottweilers "Breed only AKC registered dogs and bitches which have OFA certified hips (or HD-free hips as certified by foreign counterparts of the OFA). Imported Rottweilers must have OFA hip certification within six months after arrival in U.S.A. If semen is used from an imported Rottweiler, the dog must be x-rayed and certified by the OFA or foreign counterpart at no less than 24 months of age. Breed only dogs and bitches of stable temperament with no disqualifying physical faults according to the AKC Rottweiler Standard (i.e. entropion, ectropion, overshot, undershot, wry mouth, two or more missing teeth, unilateral cryptorchid or cryptorchid males, long coat, any base color other than black, absence of all markings.) Offer at stud with a signed written contract, only mature (two years of age or older) healthy dogs with OFA certified normal hips, free of communicable diseases, having none of the faults listed in Section 2 above. Refuse stud service to any bitch not meeting the same requirements. Breed only bitches two years of age or older with OFA certified normal hips, in good health, free of communicable diseases, having none of the faults listed above in Section 2, to not more than one stud dog at any one season, and not more than two out of three consecutive seasons. Plan all litters with the goal of improving the breed."
Saluki "To protect every Saluki from the suffering of genetic diseases, affected individuals will not be bred from."
Samoyed "Each litter is the result of conscientious planning, including consideration of the parents' freedom from hereditary defects, type, soundness, temperament and general conformance to the official standard of the breed. The SCA member must be particularly concerned with the proper placement of puppies, both pet and show potential. The SCA member only breeds healthy, mature Samoyed adults, preferable 24 months of age, but at least 18 months of age. Prior to breeding any Samoyed, the SCA member obtains certification that its hips are normal from the Orthopedic Foundation for Animals, an equivalent foreign registry, or from a board approved radiologist and has its eyes certified free from genetically transmitted defects by a certified Veterinary Ophthalmologist. The SCA member knowingly breeds Samoyeds only to other registered Samoyeds."
Scottish Deerhounds "Breeders are urged to breed only dogs and bitches that are in good health and of such maturity (yet not past their prime) to demonstrate a degree of freedom from genetic defects breeders are urged to test for health defects, where possible."
Shih Tzu "In my breeding program I will keep alert for and work to control and/or eradicate inherited problems and conditions that are particular to my breed, and breed as closely to the standard of the breed."
Silky Terriers "All breeding stock should be of sound temperament, free from congenital defects such as blindness, deafness and dysplasia. Dysplasia of the hips and shoulders may be ascertained by x-rays taken and read by a veterinarian who is familiar with the proper procedure and diagnosis."
Visla "Breed only those dogs who are free of serious hereditary defects including epilepsy, progressive retinal atrophy, von Willebrands, entropian and cranial muscular atrophy and who are over two years of age and have been xrayed and OFA certified as free from hip dysplasia."
Weimeraner "Choose only healthy parents of good temperament and qualities in relation to the Weimaraner's AKC-approved official standard, and whose hips have been X-rayed and certified free from hip dysplasia by either the Orthopedic Foundation for Animals (OFA) or any ABVR certified veterinarian. Not use dogs with hereditary defects or disqualifying faults for breeding."
Yorkshire Terriers "Prior to breeding, owners of stud dogs and bitches will adequately screen for both infectious and hereditary diseases, using current techniques as well as those developed in the future."
Money for research
The development of genetic tests is an expensive and time-consuming process. Often the same disease in two distinct breeds is the result of a different mutation. This requires a separate test for each breed. With the advent of the AKC Canine Health Foundation (include a URL here), individual clubs are able to raise money for genetic research and have that money matched by grants from the foundation. Other benefits of using the AKC/CHF are: Their ability to screen and evaluate research proposals, locate qualified research facilities, supervise and assess on-going research projects, and prevent the duplication of management and administrative functions, thus saving time and money.
Even more important than money is the raw material needed to conduct the research. This is where the individual breeders and breed clubs can make a most necessary and invaluable contribution. Without blood or cheek swab DNA samples, accompanied by accurate and appropriate pedigrees, genetic research cannot continue to advance. With this information, tests can be developed so that breeders will have the tools to make informed and responsible breeding decisions, and rectify some of the extensive health problems our dogs suffer.
It is strongly suggested that breed clubs look at the heritable diseases associated with their breeds, and establish a well-defined screening protocol mandatory for all dogs owned or bred by members of the club. The AKC Canine Health Foundation is there to help you. Furthermore, it is recommended that the code of ethics include a statement to the effect: "Members, when advertising any dog, bitch or puppy, in any venue, will include in that advertisement the genetic screening conducted on that animal and its parents." Such mandates are within the prerogative of breed clubs, and only they have the power to correct the current appalling situation of poor genetic health. It is time to stop bashing the AKC - "we are them and they are us." The responsibility for requiring genetic screening rests squarely with the parent clubs.