A useful definition of “breed” is that a breed is a group of domesticated animals that are similar
enough (usually by appearance, production, or origin) to be logically grouped together, and following mating within the group produce offspring typical of the group. That is, breeds breed true. This is a genetically-based definition, and implies that a breed is genetically uniform enough to allow for predictability of type and production.
In the animal world, three separate approaches combine to constitute breeds. Animals are distinguished first by ancestry; all of the individuals descending from a particular founder group (and only from that group) being designated as a breed. Next they are distinguished by purpose or utility; some breeds existing for the purpose of hunting particular kinds of game, others for the performance of particular tasks , at times in cooperation with their human masters, while yet others owe their existence simply to humankind’s desire for animal companionship. Finally animals are distinguished by typology, breed standards (whether written or unwritten) being used to describe and to recognize animals of specific size, physical build, general appearance, shape of head, style of ears and tail, feathering, etc., which are said to be of the same breed owing to their similarity in the foregoing respects.
The preceding statements are both obvious and known to all breeders and fanciers of most species of animals. Nevertheless, a correct and full understanding of these simple truisms is vital to the proper functioning of all animal fancies, and to the health and well being of the animals which are the object of that fancy. It is my purpose in this brief to elucidate the interrelationship of the above three approach, to demonstrate how distortions and misunderstandings of that interrelationship can threaten the health of the animals and even the very existence of the various breeds, and to propose concepts which will restore both balanced breed identity and genetic health to breeds of animals, particularly the Birmingham Roller.
In order for animal breeds to fulfill their destinies effectively, the three distinct axes along which breeds are distinguished must have equal importance and consideration. Otherwise, serious problems arise. Breeds cannot be distinguished by ancestry alone, by purpose alone, or by typology alone. Unless these three vectors of breed identity interrelate fully and cooperatively, the fullness of that identity is missing or marred. Unfortunately, this full and cooperative interrelationship is a rarity in our contemporary animal world. The criteria of ancestry are applied rigidly and mechanically; or the criteria of purpose and utility are subordinated or not considered at all; and the criteria of typology are applied in a highly exaggerated, obsessive fashion. The interaction of the three approaches is seldom considered and almost never is a sustained effort made at the integration of the three. For the purposes of this discussion, we will use dog breeds as an example upon which to illustrate their relevance to the Birmingham Roller breed of pigeon.
Canine breeds come into existence in many different ways and their beginnings are very often shrouded in obscurity. Let it not be thought that the three or four hundred-odd dog breeds that exist are the only ones possible, or that there cannot be any more truly new breeds. Such is the genetic plasticity of the dog, as with pigeons, that there is no end to the possible unique variations of which the species is capable. New breeds are born and old breeds die periodically. The genetic transformation of the dog goes on ceaselessly, and for that reason it is impossible that any breed should remain frozen, with all its characteristics fixed and unchanging, for any appreciable length of time. It must be realized that canine breeds, like pigeon breeds, are man-made; created by artificial election out of the endless diversity of the canine gene pool. Breeds must not be confused with species or even subspecies, which occur naturally under the influence of natural selection; dog breeds, again like pigeon breeds, are only unstable man-made varieties which would not survive unchanged in the natural world without human management.
An important characteristic of animal breeds is that they are created by breeders — not by registries or protective organizations such as The American Kennel Club. The origin and course of a breed is in the hands of its breeders, first, last and always. It is the business of breed associations to facilitate and support the work of breeders and not vice versa. The purpose of breed organizations, under which most breeds are incorporated, is the promotion of breed improvement and the protection of those who breed and purchase animals. All else is secondary.
Ordinarily a breed has already existed for an appreciable length of time before it reaches the point of becoming a recognized breed served by a registry. Such is true of the Birmingham Roller. Nonetheless, the event of its “recognition” by a registry is always a crucial one in the history of a breed. As things now stand, breed recognition is crucial. But before we digress into that conversation, let us examine what is needed to start a new and unique breed, such as in the development of the Birmingham Roller many years ago.
Four essential characteristics usually distinguish the origin in the genetic sense of a breed. The first and most crucial characteristic is the founder event in which a finite number of individual animals is chosen to contribute genetic material to found a unique population. They may all be quite similar, or they may be widely divergent one from another (as when Bulldog and Mastiff specimens were used to create the Bullmastiff breed in dogs). What matters is that a finite and sometimes quite small number of individuals are selected from the existing population and set apart so that their genetic material alone forms the gene pool for the new breed. That is in fact the next characteristic: isolation. If the founder group continues to exchange genetic material at random with the general population, a new breed will not result. Without genetic isolation of the new founder group, the differentiation that creates a new breed cannot take place. So the new breed of pigeon known as the Birmingham Roller could not be allowed to breed back to the tumbling breeds of pigeons from which they were derived. The logical consequence of this isolation is the next characteristic: inbreeding. If the founder group is of small or moderate size, such inbreeding cannot help but occur. Even if the founder group should be quite large, ordinarily those who guide the breeding which creates the new breed will find it necessary at some stage to employ a strong degree of incest breeding or inbreeding, to facilitate the weeding-out of undesired characteristics and the fixation of desired traits. One can envision this type of activity occurring with tumbling breeds of pigeons in the Black Country of England long ago. Particularly if individuals of widely divergent type and physique are involved, inbreeding will be required to set up a stable genome in which random variability is kept within specific limits defined by the breeders. The final essential factor is artificial selection, since inbreeding alone will not serve to fix type characteristics and to eliminate unwanted traits. The breeders must select among the individuals produced in early generations so that only those displaying the desired characteristics are allowed to produce subsequent generations. Without these four factors of the founder event; isolation, inbreeding and artificial selection, new breeds ordinarily do not come into existence. These four tools are used to define a new genome which, hopefully, contains only the traits desired by the creators of the new breed and is able to reproduce itself, with its distinguishing characteristics, to a fair degree of stability and consistency.
The Healthy Continuation of Breeds
The purebred animal kingdom is even now in serious trouble through a general failure to distinguish between what is necessary to establish a breed and what is desirable to continue that breed in perpetuity. Most registered breeds are less than a century old as registered breeds; many are but fifty or sixty years old. Yet nearly all breeds now show levels of expression of genetic defects that may be considered unacceptable. Over 500 distinct genetic defects have been cataloged in various breeds of purebred dogs and more continue to come to light regularly. Purebred cats are similarly affected. Some of these have reached very high levels of incidence, creating problems for breeders and owners, threatening the health of entire breed populations. Such is the case in many purebreds, and has been the ruination of many a Birmingham Roller stock loft. Although many breeds have developed programs designed to successfully identify affected animals, in some cases individuals with several generations of “clear” ancestry stubbornly continue to produce affected undesirable stock. Let us try to examine what has gone wrong and what must be done to correct the situation.
First of all it must be recognized that practices which were essential for the differentiation and establishment of a new breed may not necessarily be desirable for its continuation over time and may in fact be prejudicial to a breeds continued existence over the long term. Let us take isolation, for example. Without genetic isolation, it would not be possible to control the genome of a new breed still few in number. It takes time and careful breeding to fix a new combination of characteristics; while that is being done, the regular addition of new genetic material would generally be counterproductive. Yet in the long term, if genetic isolation is maintained, it will necessarily lead to degeneration through genetic drift. Similarly inbreeding, if it continues to be practiced after the need for it is past, will lead to a steadily increasing state of homozygosity which may well destroy the genetic health of the new breed. Genetic recessive traits rarely seen before will become evident and threaten the viability of the breed. Even artificial selection, if carried on too strongly for too long, can combine with isolation and inbreeding to reduce drastically the effective breeding population, thus eroding the genetic health of the breed.
The Fallacy of Breed Purity
The present structure of pedigrees embodies a fallacy which is directly responsible for the current genetic crisis in purebreds: the fallacy of breed purity. The ideal of the purified lineage is seen as an end in itself; accordingly, the pedigree has been structured to reflect and to enforce that ideal rigidly and absolutely. This insistence on absolute breed purity arises from nineteenth-century notions of the “superior strain” which were supposedly exemplified by human aristocracies and thoroughbred horses. This same ideal, pushed to an illogical conclusion on the human plane, resulted in the now discredited “scientific racism” of the Nazis, who tried through selective human matings to breed an Aryan superman. The idea of the superior strain was that by “breeding the best to the best,” employing sustained inbreeding and selection for “superior” qualities, one would develop a bloodline superior in every way to the unrefined, base stock which was the best that nature could produce. Naturally the purified line must then be preserved from dilution and debasement by base-born stock. There is no support for this kind of racism in the findings of modern genetics — in fact, quite the opposite: population groups that are numerically limited and closed to new genetic inflow are now thought practically certain to be genetically inferior. Certainly towards the close of the nineteenth century it became embarrassingly obvious that the human aristocracies of Europe were degenerating rapidly under their own version of the “closed studbook.”
The ideal of breed purity as applied to purebred animals has resulted at the end of the twentieth century in a subculture that holds “purebred” registered animal stock to be qualitatively superior to crossbred or “mongrel” stock. (The word “mongrel” is in fact part of the vocabulary of racism, being applied equally to animal stocks of no recognizable breed, to animal crossbreeds, and to persons of mixed race!) In this subculture concept, it is thought to be of paramount importance that purebred stock be maintained unsullied by any genetic influence external to the supposedly superior strains that are produced by registered breeding in a closed studbook from a small group of foundation stock. And it is applied to nearly all animal breeds, not only pigeons. New members of these breed registries are required to subscribe to “Conditions of Membership” whereby they promise to have nothing to do with animals which are not “purebred” (with the exception of family pets and boarders); “purebred” being specifically defined as referring only to animals “registered individually” (or eligible for registration), or those with “proven” pedigree records. Offspring which are made the subject of complaints that they may not be purebred are investigated in some breeds of animals, and in many cases, ceremoniously withdrawn from the registry by resolution of the Club’s Board of Directors. Whether you like the word or not, this is effectively a special variety of “racism” in concept and in practice applied to animals.
Not all animal breeders are in agreement with the proposition that breed purity is more important than anything else, particularly when they are confronted with the problem of breeding animals to demanding performance standards. Mostly such dissenters are obliged to carry on their breeding without the benefit of centralized pedigree record keeping and official certificates of registration — for example, those who breed “Alaskan huskies”, the high-performance racing sled-dogs that dominate both short and long distance dogsled racing, keep pedigree records and maintain sophisticated breeding programs, but only as individual breeders. Similarly many breeds of Birmingham Rollers maintain their pedigree lineage back to the original Pensom imports. Yet sometimes participants of established purebred animals (including Birmingham Rollers) engage in a subtle kind of rebellion, quietly breeding (even Birmingham Rollers, regardless of color) to their own superior judgment and performance standards in defiance of conventional restrictions maintained by those committed to breed purity. Thus the Racing Greyhound Club of Australia, when it recently subjected a broad sample of stock from its registry to DNA testing, is rumored to have discovered that many pedigrees failed to match DNA ancestry findings and that considerable interbreed crossing had apparently occurred. Similarly most Siberian Husky fanciers are aware that some Canadian Kennel Club bloodlines may have received surreptitious infusions of genetic material from non-purebreds or from other breeds. Likewise we have seen this with the Birmingham Rollers for the purposes of importing colors and modifiers. In some circles one even gets the distinct impression that it’s OK to crossbreed occasionally if you have a good reason for doing it and you manage it in such a way that no embarrassingly obvious mongrels are produced; if ones breeds back to the original purebreds for the genetically accepted eight generations; or if one “just doesn’t get caught!” Thus the sanctity of breed purity may sometimes be less than inviolate in actual practice, especially when breeding occurs in animals that are housed randomly and openly.
More important than idealistic notions of breed purity, population geneticists insist that limited populations under strong artificial selection, subjected to high levels of incest breeding simply cannot maintain genetic viability and vigor in the long term without the periodic introduction of new and unrelated genetic material. They are referring, moreover, to true outcrossing, the introduction of stock unrelated to the breeding line, not merely the use of an animal which might be from someone else’s stock that is, in fact, derived from exactly the same foundation stock some generations back.
DNA research has radically changed zoological concepts of species, subspecies and varieties. In the nineteenth century and the first half of this century it was thought that a species could be represented by a type specimen, that the vast majority of individuals of a species were virtual photocopies of the type specimen, genetically speaking, and that the genetic norm for most species was homozygous at most loci. In the mid 1960s the credibility of that idea was shattered as electrophoresis protein studies revealed extensive protein polymorphism that had not been previously suspected. Today the concept of a species in a satisfactory state of genetic health invokes a state of “dynamic balance” in which the species genome contains an array of genotypes with a high degree of heterozygosity, with multiple alleles at many gene loci. Natural selection is now thought to favor heterozygotes in a way which tends toward a high state of natural variability, preserving the greatest variety of possibilities with which a species can meet new environmental challenges. Conversely, species which have lost most of their genetic diversity, often through accidental population “bottlenecks” are held to be in high risk of extinction through the loss of adaptive capability, resulting in susceptibility to disease lack of parenting skills, etc. (The most notorious example is the cheetah, which is almost totally homozygous and is thought to have undergone at some time a bottleneck reducing its population to a tiny handful of specimens.)
There is no reason why domestic animal breeds also cannot be maintained in a balanced state of heterozygosity, analogous to that of healthy wild animal species, if typological thinking could somehow be replaced (or at least tempered) with population thinking. Fanciers will generally admit that, in reality, few animals conform perfectly to its breed standard, though this does not diminish the establishment of bred registries in any way. Thus the concept of the perfect type specimen, to which an entire breed ought to conform as closely as possible, is really as foreign to domestic animal breeds as it is to animal species in the wild. We see this in our own Birmingham Roller fancy in which rollers of a wide variety of types and colors are known to perform to standard.
The fanatical pursuit of breed type to the exclusion of other more important factors has led to a distinctly unhealthy situation in many breeds. Since the majority of breeders seem to direct their efforts toward the production of a winning exhibition or performance specimen, a situation has arisen in which continued effort to produce winners leads consistently to greater and greater exaggerations of certain factors most susceptible to success in competition. It is an accepted fact that strong incest breeding is the fastest route to this kind of “success”. In the dog world, here is one successful show breeder’s recipe for “excellence” [de Boer and de Boer, DOGS in Canada, April 1994]:
“My approach would be to identify an outstanding, dominant stud dog. Let’s call him ‘Shadrack.’ To improve the odds I’d buy or lease three bitches whose grandsire on the dam’s side was the same as Shadrack’s sire. Let’s call the grandsire ‘Fashion Hint.’ I would breed the Fashion Hint bitches to Shadrack. Assume, in this first generation, that I get three nice bitches. For the second generation, I’d breed them to a half-brother of these three bitches (Shadrack’s son, also a dominant sire). For the third generation, several ‘mix and match’ options include going back to Fashion Hint or Shadrack. I would also do brother-to-sister or father-to-daughter breeding.”
Thus the quest for more and more refined breed type or performance leads directly to a state of advanced homozygosity, rising inbreeding coefficient, low effective breeding population and consequent impoverishment of the gene pool in most breeds, through rampant uncontrolled line-breeding . This sounds all too familiar to the concept of “ pretzel breeding”, the commonly recommended practice for breeding the Birmingham Roller.
The show ring has been largely responsible for the decline of breed purpose, working ability and temperament in a great many breeds, notably performance breeds, as we have seen in the past in Birmingham Rollers with the Show Roller fiasco. The quick and easy gratification of blue ribbons and gilt trophies all too readily supplants the hard work necessary to preserve and advance performance abilities. If our breeds are to conform to the ideal, the fancy must find some way of ensuring that, less pigeon-breeding takes place along the lines of least resistance and cheap gratification, so that greater attention is paid to performance, as has been the case in recent decades. A balanced outlook on breed identity must be restored by integrating performance with the ideals of conformation, beauty and “type.” Those aspects of the fancy should be accorded an importance fully equal to that of type and conformation instead of being regarded as merely optional. For example, breeding and exhibition of rollers merely for sale, with no effort made to maintain and advance their performance, is an obvious abuse which must lead inevitably to mental and physical degeneracy in the breed.
Abandoning Natural Selection
The breeder of domestic stock often assumes that he has abandoned the realm of natural selection and that only artificial selection plays a significant role in his breeding program. Nothing could be further from the truth. The breeder may attempt to abandon natural selection; natural selection, however, will not abandon his stock. As one geneticist puts it:
“Man-imposed characteristics, however, like the flower colors and forms selected by the plant breeder, usually do not perturb the deep-set genetic variability systems of the species. Most such changes are reversible when a less restricted gene pool is restored. The ‘balance’ system appears to be retained by natural selection, which, perhaps paradoxically, pervades most systems of artificial selection.” (Hampton L. Carson, The Genetics of the Founder Effect. l983)
Those who attempt to set aside the balanced genomes arrived at by natural selection must struggle thereafter to attain and to maintain fitness in their stock. Artificial selection alone involves breeding in a way which flagrantly disregards most of the gene loci in the genome. Since genes assort in groups on chromosomes (a phenomenon known as “linkage”), inbreeding and selection for desired traits unavoidably affect many other genes which are inadvertently selected and often fixed in a homozygous state in total ignorance of what is happening. This may be a major factor in the prevalence of genetic diseases. Thus natural selection, baulked for a season by artificial selection, high-level nutrition, and advanced veterinary care and medications, reasserts its primacy at a deeper and more serious level when the new genome as set up by the breeder proves flawed through genetic unsoundness, so that healthy and hardy animals can no longer be produced, however typey and attractive to the eyes of the judges the resulting performance may be.
As genetic variability diminishes and homozygosity rises through inbreeding, a syndrome known as inbreeding depression sets in. It is characterized by a reduction in viability (survival of individual progeny), birth weight, fecundity (number of young) and fertility (reproductive success), among other things. Much of it is caused by the homozygous presence of rare, deleterious recessive alleles. Part of it may also be due to the relative absence of over-dominant heterozygote combinations. As inbreeding depression becomes more severe, highly inbred lines tend to become extinct through the loss of ability to reproduce successfully and / or inability of the young to survive. It varies somewhat in intensity from species to species, due probably to variations in the number and nature of lethal, sublethal and subvital alleles involved. Some wild mammals which show almost no juvenile mortality when bred in captivity without inbreeding, exhibit 100 percent juvenile mortality when inbred! A survey of captive breeding records for 44 species [Ralls & Ballou, 1979, 1982] showed that juvenile mortality of inbred young was higher than that of non-inbred young in 41 of the 44 species for which records were analyzed.
Declining vigor caused by the inadvertent fixation of sublethal and subvital alleles will not be made up for by any number of Master Flier points, plaques or trophies. Fitness criteria may not be replaced by esthetic or performance criteria. The animal’s environment is the ultimate arbiter of its fitness and will not be denied its say. You may vaccinate your birds and dose them with antibiotics, feed them vitamins and minerals as you like, or enclose them in a sterile pathogen-free laboratory environment if it comes to that! Still natural selection cannot be avoided; it only emerges at a deeper level. In a sense the bird’s environment includes his own physical body; if the genes which blueprint his physiology are flawed, then he is doomed regardless of his beauty, classic breed type, or performance qualities. The truth is that the “superior strain” cannot be produced by manmade breeding programs and artificial selection; the breeder’s decisions are subject to nature’s veto at all times.
With what, then, will the breeder replace natural selection? If he replaces it with a profit motive, the degeneracy of his stock will in the end put him out of business as veterinary costs and death eat up his profit margin. If he replaces it with shows and trophies, in the end his beautiful contest winners will engender weaklings and degenerates. If he replaces it with screening programs for the “elimination of genetic defects,” in the end his stock will succumb to inbreeding depression as hens fail to lay eggs, to parent naturally, and squabs die in the nest. If he replaces it with veterinary care, in the end his stock will die prematurely of incurable cancers, or the young will fall prey to viral diseases despite repeated polyvalent vaccinations. If he replaces it with work and austerity, his stock may endure awhile longer, but in the end it will turn out to be afflicted with genetic ills that slipped through his demanding program, or its performance will mysteriously decline as the inbreeding coefficient creeps upward. In the end, natural selection cannot truly be replaced with artificial criteria. The breeder must find a way to work with natural selection, within the framework of what is now known about the biological operation of the natural world. We in the roller fancy must begin to take lessons from wildlife biologists, from evolutionary biologists, from population geneticists.
In our quest for breed purity, the superior strain, the classic type, the optimum spin, we may ultimately make a sad mess of our birds – with neurotic temperaments, blindness, deafness, immune system weakness, skin diseases, blood disorders, endocrine system malfunctions, crippling blood disorders, deliberate deformity, and often even the inability to reproduce their kind without breeder and veterinary intervention. How clever we will have been!
Can we not now take a clear-sighted view of the potential of what we may do; of our own pitifully-flawed creations in our world of pigeons and, like mature, intelligent people, try to do better? If we would be truly clever, we might attempt to imitate more closely the methods of nature, to work within the natural system, albeit for our own ends. That would indeed be clever. I think that that is now possible, if we would but step outside our own incestuous little purebred world and learn something of what people working in other zoological fields of endeavor have already learned.
More commonly known as hybrid vigor, heterosis is a situation in which a cross of two or sometimes three highly-inbred bloodlines displays enhanced performance for some desired trait, as for example higher yield in corn. It works best in plant species capable of self-fertilization, but has been amply demonstrated in domestic livestock species. It is worth noting that in practice many different inbred lines must be developed at the same time, and that considerable random trial of different crosses must be done to establish which lines will actually yield the desired result. Although the seed-grower’s methods are unsuited to breeding rollers, the overall principle is of interest, since it is thought that heterosis works because of the heterozygosity of the hybrid generation, probably through the action of both dominant and over-dominant genes. Geneticists are now starting to realize that the balanced-heterozygote systems of many wild species involve a heterosis effect which gives them a high degree of fitness.
At the beginning of this brief I stated that the three distinct axes along which breeds are distinguished — ancestry, purpose, and typology — had to relate fully and cooperatively, or the fullness of breed identity would be missing or marred. Let me now describe how such a relationship might he achieved.
To begin with, we might consider opening pedigree books, in every family of rollers, to new genetic inflow. There can be no long-term genetic health in small populations without the periodic infusion of new genetic material. The one big “sacrifice” we shall have to make, if it is really a sacrifice, is to abandon racist attitudes and the concept of rigorous breed purity. We must recognize that first of all, a roller is a pigeon, species Columbae livia, and that is their true identity. They are pigeons first, before he they are Jaconettes or Pensoms; family identity is subordinate to species identity. We must stop treating families of rollers as if they were species, abandon the rigidity and narrow typological thinking which has heretofore characterized the roller fancy. We must recognize that, although pigeon families are unique, there is, in reality, no positive value in trying to sustain families or groups of rollers which are all clones or photocopies of a type specimen represented by a performance standard. This should not be too hard, since breeders and judges have never been able to arrive at agreed and consistent interpretations of breed or performance standards anyway. Why, then, should we pretend that a standard, which as it now exists evokes a different interpretation in the mind of each individual breeder and judge, describes a single ideal family?
Families of rollers can and should be differentiated, bred and maintained on a dynamically balanced, heterozygous population basis without restriction to a closed, historic founder group. The closed pedigree book and the breed purity concept are, from a genetic point of view, simply unnecessary. Indeed, as we have seen, from the standpoint of maintaining a genetically healthy limited population, they are thoroughly counterproductive. Where is the logic in submitting each and every family of rollers to a registry system based on purity which guarantees ongoing, progressive genetic degeneration, loss of species vigor and hardiness, and saddles every breeder with the unwanted, unhappy responsibility of producing more and more, unhealthy, flawed stock as time goes by? The notion that genetic disease can be controlled or eliminated by screening programs and selection is a concept whose time has come, but may not be born out by general experience in the end. It may be that a breeder can sometimes improve his odds against producing defective stock in a given mating by screening the parents, but screening through culling or testing may not solve our genetic problems in any wider sense. Despite generation after generation of “clear” stock, bloodlines can still produce more and more affected animals. That is because our problems are inherent in the closed studbook/incest breeding system. In order to restore genetic health we shall have to adopt a different system.
It will be asked, “Just how will the opening of our studbooks to outcross stock bring about the elimination of genetic defects?” The answer is that it will not eliminate genetic defects. That need not be the end in view. If we could somehow eliminate all the various genes now known to produce harmful anomalies, plus all of those yet to be discovered, we would almost certainly find that the remaining genome was non-viable, that healthy reproduction and growth to maturity could not reliably take place. Genetic defects are not “eliminated” in nature. Instead random mating and behavior patterns that discourage inbreeding take care of the problem by ensuring high levels of heterozygosity and the consequent rarity of defective homozygotes. If we take steps to set up similar patterns in families of Birmingham Rollers, we shall be able to reduce the level of expression of defective genes greatly, which is all that is required. The end in view is healthy stock, not “racial purity.” Purged and purified bloodlines would be weak for other reasons, as has been explained. Now, with the mapping of the pigeon genome and RFLP microsatellite “markers” for common genetic defects are found, we shall probably then be able to use DNA studies to recommend matings that will avoid the production of defective homozygous progeny — provided that we have made enough genetic diversity available through outcrossing to give us the genetically distinct lines from which to choose! As things stand now, some families may already be so homozygous that it could prove extremely difficult to find matings which would avoid one genetic defect without reinforcing another!
I can hear someone objecting, after having thought about the idea of a breeding and registry system in which outcross breeding was actually encouraged, “Surely this system will produce rollers which are not even recognizable representatives of their breeds, or lack the performance qualities we value! What happens then?” Typological thinking dies hard. I used to worry lest my breeding program should one day produce a pigeon with crests, feathered feet, or thirteen tailfeathers. It never happened. Let me say the following, then, to those who worry that a balanced-heterozygous breed will engender “untypical” examples. It is far better that our breeding occasionally engender a pigeon slightly deficient in breed type, than that we should consistently produce large numbers of pigeons guaranteed to lead lives of suffering, creating anxiety, large veterinary bills, frustration and unhappiness for their owners. That is what we are doing now with many breeds if animals. Over sixty percent of Golden Retrievers, for example, will suffer from hip dysplasia, osteoarthritis or osteochondritis in their lifetimes. Is that to be preferred to the possibility of producing an occasional robust “mutt” lacking in breed type but who will nonetheless still make someone an excellent happy, healthy companion? I am sure that it would take awhile for all of us to learn how to breed in this new and different way; I suppose we might produce occasional odd type in the process. But we already do that. And I am absolutely convinced that the good results we would quickly achieve would more than make up for the embarrassment of our failures. At the very least we should all have clean consciences once again, knowing that we were making our best efforts, using up-to-date genetic knowledge, to produce sane, healthy, robust roller populations. Let us not forget that as DNA mapping procedures advance, our tools are going to improve and our ability to predict what our breedings may produce will be greatly enhanced.
Change within the fancy cannot occur without widespread debate among fanciers, because new and different concepts sound threatening when they are first described. But this is not really so new a concept. Many fliers already engage in regular outcrossing in the name of creating their own unique family. The whole idea of a dynamically balanced heterozygous breeding system is the retention of as much healthy genetic diversity as possible, and already occurs in many lofts. Such diversity makes it easy for a breed to develop and progress in whatever direction its breeders wish. It also ensures that genetic problems are kept to a minimum no matter what changes of standard may occur. In the statically balanced homozygous system now in force within many other lofts, the more homozygosity increases with time and selective breeding, the harder it becomes for major change to occur naturally and easily, and the more pronounced genetic problems become. Once an allele has been “fixed” in homozygosity, no amount of selection can change that trait; only radical outcrossing can restore the lost alleles and such outcrosses will always upset the static balance completely, necessitating years of remedial inbreeding and selection, probably creating new genetic problems. I am convinced that a system based on a dynamic equilibrium of healthy dominant genes must inevitably be better than one which throws away most of the healthy genetic diversity in order to achieve static stability for homozygous recessive traits.
Inevitably some will feel that the suggestions contained in this brief are unrealistic and impracticable, that ideas such as breed diversity and balanced-heterozygous breeding “will never fly”. Many breeders will reject outright the mere idea of deliberately trying to increase heterozygosity, after so many years in the pursuit of homozygosity through “linebreeding” and inbreeding to enhance performance and increase the consistency of its production. Just now, our hope and effort rests upon research towards detection of DNA markers for major genetic diseases, for performance, and for strain identity. A breed’s gene pool may be likened to a bank account: one cannot go on making withdrawals forever without an occasional deposit (no matter what deficit-spending politicians may think). It is far too easy to ignore genetic predisposition for diseases, to make excuses, to buy the medications, to pay the vet bills and say nothing for fear that others will accuse one of breeding defective stock. Yet the truth is that we may be breeding defective stock; the system itself virtually guarantees that. If we believe that to breed defective stock is a bad thing, then we simply must discuss ways and means of altering that system to allow us to restore genetic health. We must now seek to evolve a system which will naturally, almost automatically, produce healthy animals — so that we may continue on with our selection for temperament, performance, and breed type. Most of all, it is imperative that we start now to discuss and work on the new systems that are needed to facilitate genetic health for our birds.