Many GSD fanciers (yes, unfortunately even breeders) have either not heard of the Zuchtwert program or have almost no idea of what it is. For nearly four decades, the world of dogs has known about canine hip dysplasia (HD) and has followed protocols laid down in the 1950s and ‘60s for diagnosis and control. In the U.S., pedigree registration has been taken over by AKC, UKC, and other organizations while the primary focus on dysplasia has been on and by the OFA; in Europe and elsewhere, the breed clubs have the responsibility for both registration and disease control. In both, the methodology of diagnosis had been basically the same: a ventrodorsal radiographic view with the dog’s legs stretched out straight. This has proven to be of great value in detecting DJD, degenerative joint disease, but only of limited usefulness in discovering joint laxity (the primary precursor to DJD, and another definition for HD). Since dog breeders and buyers have become dissatisfied with the lack of suitable progress, we have looked for some advance that would enable us to rise above this plateau we have reached with the old methods.
In North America, where HD control is in the hands of the individual, the great advance to help us climb to the next level is the improved diagnostic and predictive technique known as the PennHIP distraction method. In Germany, the new and (almost as) great leap forward is the adoption of the Zuchtwert (ZW) program by the SV. The English translation would be “Breed Value (BV)”. The SV leadership in recent years realized that something had to be done, because the incidence of HD was stagnating at an still uncomfortably high percentage. They hired Prof. Dr. Reiner Beuing of the University of Gießen. Much of the information in this article is a result of my personal correspondence with him and my translation of his articles in 1998 and 1999 issues of the SV Zeitung, 1998 bulletins, plus the special HD and other news that I, as an SV conformation judge, get from the SV. In some parts of this, I will be paraphrasing Dr. Beuing.
In its general meeting in May 1998 in Leipzig, the SV unanimously agreed upon the introduction of the Zuchtwert evaluation and the publication of this knowledge to support a breeding program for the fight against hip dysplasia. The delegates at the SV National Meeting in 1999 again unanimously confirmed the implementation of this “Breed Value Assessment” (ZW). Thereby, the SV took the first step on what was incorrectly called an untrodden path. It actually is an old cattle-breeders’ approach, and some organizations had been using it for a long, long time. But it is like the Vikings or Columbus telling the Indians that they (the Europeans) had just “discovered” the new world, when it was no new discovery at all to those already living here. The Seeing Eye, Inc.® has long used BV in their selection of good hips and other qualities desirable for guide dogs. Even in Germany, the ZW concept had already been adopted by other breed clubs, but it took the deliberation and then the determination of the sleeping giant (SV) to make a statistically significant impact in changing hip joint quality and genetic improvement. The path has been planned and mapped conscientiously and thoroughly by the committees of the breed control and the technical sections of the headquarters; nevertheless it is still up to the practical breeder to go along this path and to trust it. The SV has made ZW a component of the breeding rules (Zuchtordnung).
Individual animals do not always reproduce themselves as we often hope. It is common experience in the breed scene, that some show winner, performance star, or other champion or typey dog produces disappointingly, while on the other hand, an almost dreamlike ideal, normal, “to-the-standard” dog often results from an accidental breeding. Similarly, one must understand that a healthy dog gives no guarantee that his progeny will be healthy. HD, elbow dysplasia, epilepsy, eye disorders, etc. unexpectedly arise from apparently normal parents, and catch most breeders unawares. Then if characteristics can be different in the breeding animal than in its progeny, one must wonder why have all these breed surveys and breeding requirements? And how can we set it up so that the phenotypes of those animals can tell us how they will probably produce?
Each breeder tries to include already-available information concerning siblings and his own experience with other progeny. No breeder can put forward a really objective picture, however. Additionally, there is the tremendous abundance of dogs in the breed, and no one is in the position of getting and cataloging their achievement tests or health control data, not with well over 30,000 puppies born annually. So up to now all we could do was consider only the stud dogs or the breeding bitches themselves. Today, however, the time is ripe for more. Computer technology and the information revolution have matured so that the club (SV) can document not only all members, but also can give clues regarding how good the dogs themselves should be, and how they will probably produce.
Definition of the Breed Value
Breed Value Assessment (Zuchtwert) is the attempt to describe how an animal will pass characteristics to its progeny. Hereditary transmission (whether improving or weakening) is described to breeders as “value or breed worthiness”, and is expressed in the form of a number. An animal bequeathing an “average” value (neither improving nor worsening) has a value of 100. Animals that improve upon this average in the breeding scheme (in HD that would be lowering the incidence in progeny) are given value numbers under 100; animals that magnify or increase the feature will have values over 100. With this system, the breeder need no longer focus [as much?] on whether a particular dog is free of HD, or what degree of laxity/tightness it has; in the future he can expect a reduced risk of HD (smaller ZW number) or an increased risk (high number).
We thus have numbers that tell us what the animals’ phenotypes or performances are like. For instance, the score earned in tracking work tells us whether the dog was good or bad. We have numbers about the size (shoulder height), and points on gait or type. In many features there is a numerical value, which tells us how pronounced the characteristic is. As breeders, however, we need a number that tells us how pronounced the feature in the progeny will likely be. In other words, use phenotype and progeny testing to give a better clue as to genotype. This number, to be applied to the breed, is called Zuchtwert (breed value). There is therefore, for each feature, one phenotypic measurement and one genetic breed value. As concerns HD, (unquestionably the most urgent ZW trait considered by the SV) a breed value is to be published from now on for each dog. The fight against hip dysplasia is of great concern in the German Shepherd Dog. As the world’s most populous breed, its name is brought up again and again in connection with hereditary diseases and breed faults. One may lament that as being unjust, because in other, smaller-population breeds there are much higher percentages though the absolute numbers are less conspicuous. However, whining complaints and rationalizations are of little use. There is an old maxim: the larger and more striking a picture of oneself that one presents to the public, so much better must he actually be!
With this explanation, the definition of the breed value becomes understandable: it is a numerical value to be applied to the breed to describe the effects that the genes have on a trait, compared to the genes of the rest of the population and the effects of normal environments. We must emphasize first of all that the breed value has nothing to do with how valuable or worthless an individual dog is, but is only a numerical value describing if the genes working on this trait strengthen (improve) or weaken it for the next generation. For diseases, that means that high breed value numbers indicate a worsening of what the breeders see as undesirable re the disease or anatomical construction. The goal must be to introduce breeding animals that reduce the disease risk in the breed. Low numbers are therefore more valuable in such cases! With other traits, such as outstanding predisposition for high drives, we would take high ZW numbers as being prized or desirable. With height at withers, it is not that simple. A high breed value for a dog in this instance means that his genes increase the size. That can be valuable and important for a small bitch. For a bitch already over the limit, such a dog is not recommended. It is up to the breeder to use his best judgment to select the suitable dogs for his bitch, and it is best if he first knows what the breed values are.
The Relative Breed Value
If one is to advertise or publish breed values, they must be easily understood. An HD breed value of +0.14 means for example, that with an equivalently-rated partner, the offspring probably will be 0.14 (HD degrees or points) higher. This is unwieldy; therefore, breed values are not expressed as absolute numbers, but as relative to the breed cross-section. Therefore we take 100 (points) for the breed level (as typical or average). Dogs with ZW over 100 increase (worsen), while those under 100 reduce, the characteristic. A technical point, but to be stated despite my recommendation to forget about it right away, is that the variation from the median amounts to 10 points either way; this means that a reported ZW of 90 should be read as a range of 80 to 100. Thus, if a bitch has a breed value of 95 for HD, one knows that she can improve the breed, but a dog with ZW of 115 exacerbates the HD problems. By referring to breed averages, the classifications regarding different characteristics also become comparable. If we get, for example, a dog with HD 92 and shoulder height 108, this makes it clear that he is a breeding partner that can be used for improving the HD scores and increasing the inherited size trait.
Why is Breed Value Median Always
Only an Estimate?
One finds, in the biology of inheritance, that we can determine the true breed value only with difficulty. The owner’s personal, subjective judgment of his animals is not a 100-percent reflection of the genes; therefore we recommend the use of breed values. The ZW number is not a mathematically precise guarantee of genetic constitution because:
The genes work only in the particular individuals themselves and not in concert with the genes in the rest of the population (there can be, for example, action of concealed recessive genes that do not show in others).
Environment certainly influences the expression of the genes in these animals.
Both reasons (for ZW being only an estimate) give a false picture. The reliability with which one can recognize the true breed value from the appearance (phenotype) is, for instance, around 20% for HD, for shoulder height around 50%, etc. One calls this percentage heredity and/or heritability. [Note: Such heritability figures are not always backed up with scientific studies and professional, peer-reviewed journal articles. For example, OFA has given 0.25 as the heritability of HD but has never produced any evidence to back this up. Meanwhile, organizations such as the University of Pennsylvania and The Seeing Eye, Inc. have concluded with reasonable reliability that the PennHIP diagnostic technique gives a heritability figure of over 0.4, meaning that their method is considerably more “telling” than the leg-extended views used by SV, OFA, GDC, etc. Heritability varies with breed, diagnostic technique, even a person’s own strain of bloodlines.]
Each animal receives his genes from father and mother, half from each one at random. Information about siblings or progeny is thus based only on a random gene sampling from the contribution of the parents. First, the statistics allow us to get an approximate picture from abundant knowledge and/or observations. A spoonful from the stock pot gives only a chance picture as to how many “chunks” and how much “broth” are in the stew, and each additional ladle shows us more accurately how rich the soup is. So also our knowledge about the genetic “capacity” of a breeding animal increases with each additional litter he or she produces.
Present Standing of the Knowledge
Breed values help decide many things: whether to use a stud dog for a given bitch, a breed survey, a puppy sale, if the puppy should become a breed dog, and yes, even before birth, since the question is put as to whether subsequent puppies are themselves programmed for life by their genetic portion. All available information must be used to bring us to the knowledge needed to make an estimated breed value (ZW). Estimated breed value means “the most probable genetic production, as determined by the current knowledge”. Since in the course of time more knowledge is always forthcoming, certain limitations of the ZW estimates will also change. Several have made comments such as, “It is not clear how the SV arrives at the ZW-HD numbers. Until we know that, the ratings are less valuable than they should be, despite SV regulations.” Certainly, there is a need for the SV to do more about the limitations of the system and its interpretation, but it is still a big step forward; there is also a need for breeders to support such programs. Dr. Beuing presents the picture of this need as consisting of half a dozen or so “levels of knowledge”.
First level of knowledge
From father and mother ZW estimates, we can make some statements about what genetic contributions may exist. Since father and mother each bring in half of the genes in each of the puppies, and the effect of these genes is described by the breed value, then for the calculating of ZWs of the puppies, it must be 1/2 the sire’s breed value plus 1/2 the dam’s breed value. This is the same as saying you can add the ZWs of sire and dam and take the average (divide by 2) to give the starting ZW for your dog. Once a dog gets out of Germany, however, no matter how good his hips or non-German progeny, his ZW will remain the same. Only those producing in SV-registry countries can change their ZWs by virtue of producing good-hip offspring. The better the breed values of the parents are, the more favorable the probable genetic make-up (ZW) of the puppies!
Second level of knowledge
While one can learn the ZW even before the actual mating, dogs can also be evaluated and “scored” by using data on earlier litters of these parents. These siblings can improve the evidence about father or mother and their “progeny-correcting” breed values. Breed values for individual puppies thus can be known somewhat, without physically evaluating the puppies themselves.
Third level of knowledge
At the beginning, the level of knowledge was derived only from the breed values of the parents, which with time and more progeny become increasingly more accurate. Since all puppies of a litter have the same parents, all puppies must also begin with equal estimated breed values. Each puppy however has received respectively half from the father’s and half from the mother’s genomes. By sheer good fortune, a puppy thus can have received more favorable genes than have his littermates. This “distribution of good luck” or “distribution of bad luck” at the stage of cell combination and development of the egg and sperm leads to the fact that full siblings can considerably differ genetically [as well as phenotypically] in their particulars. Whether an individual animal is blest or cursed by the random allocation, for instance in reference to the HD genes, can be estimated only if the animals are radiographed for HD. The picture depends on “egg & sperm contribution” but also on environmental factors, radiographic technique, position, and subjective judgment.
Fourth level of knowledge
If full siblings also get evaluated, and especially if most are assessed quite close to the time that the animal of interest (called the “proband” or “probationer”) is under consideration, then their “declarations” supplement the breed values of the parents and also indirectly the breed value of the “probationer” (your dog, for example). Breed values thus can change further after individual appraisals, even if a dog is never used in the breed.
Fifth level of knowledge
If the animal does come into the breed’s gene pool, his genetic continuity becomes effective in his progeny, combined with different breeding partners. With each examined offspring, the knowledge climbs in importance beyond his own former ZW. The estimated values themselves vary from the average of the [original] breed value. With each puppy whelped, points begin again for another first level of knowledge, so that the breeder comes full circle and starts all over again with each litter.
If a descendant is evaluated, he gives knowledge about father and mother. The father will bring such information to the descendant that is not clearly provided by the mother, and the mother contributes only that which is not donated by the father. The following simple situation should serve as example:
I import a dog and a bitch; nothing is known about their relatives. A litter from these reveals bad HD results. Since the placing of blame on only one parent is not possible, both receive uniformly and equally a bad breed value (e.g., 110). The bitch whelps a second litter sired by a frequently used stud dog with a ZW of 89 (he already has 80 offspring, 30 of them radiographed, with predominantly good hips) and we find again that she produces medium and severe HD. Now, the transmission of many bad genes by the bitch becomes evident through this second pairing, because with a known good-producing dog she has undesirable results! Her breed value index drastically rises thereby. And that has consequences for further use of the imported stud dog that was the sire of the first litter. He is exonerated, and can possibly get 100 or under, even if he personally has no further progeny.
Breed Value Assessment (Zuchtwertschätzung) does not claim to document the truth about the “genes”. But it should give indication of the presence of good or unfavorable genes. The breeder urgently needs these signs. He must build his kennel with the foundation of genes from the best families, and take all indications of problems under consideration, be they HD, size, character, working ability, etc. When breed clubs offer instruction through this Zuchtwert assessment, at least for some feature urgently in need of attention in the beginning, the breed will develop quickly in the desired direction. Since 1989, Zuchtwertschätzung has been used in other clubs, with subsequently developed breeding programs, but also for non-binding information.