Why is Breed Value Median Always Only an Estimate?

One finds, it 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;

1. 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).

2. 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, hald from each one of 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 ech 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 whetehr 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 ZW estimates will also change. Several have made comments such as, “it is not clear how the SV arrives a the ZW-HD numbers. Until we know that, the ratings are less valuable than they should be, despite 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”.

Fist 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 conscribed by the breed value, then for the calculating of ZWs of the puppies, it must be 1/2 the dam’s breed value. This is the same as saying you can add the ZWs 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 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 shet 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 generically [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. 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 “declaration” 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 very from the average of the [original] breed value. With each puppy whelped, points begin again fro another first level of knowledge, so that the breeder comes full circle and starts all over again with each litter.

Further knowledge

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 result. 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 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.

The claim

Breed value Assessment (Zuchtwertschatzung) does not claim to document the truth about the “genes”. But it should give indication of the presence of good of 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 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, Zuchtwertschatzung has been used in other clubs, with subsequently developed breeding programs, but also for non – binding information.

ZW Mandatroy As of july 1999

Wide implementation of the method of breed Value Assessment has been effective in the “Commercial animal” breeds (food & textile). This includes, in a computer record, all available data of the ancestors and any available progeny as well as of the personal phenotype of the animal concerned, and can work authentically and exceedingly effectively in the purebred dog. In cooperation with the institute of breeding Animal Genetics at the University of Gie?en, the SV developed a breeding program that became obligatory as of July 1, 1999. before that starting in September 1998, the process was voluntary. Each breeder currently and henceforth knows about the inheritance (HD production) risk of his bitch through this HD breed value. The breed value numbers of all stud dogs are likewise disclosed. From both of these sides comes a greater knowledge of HD risk for their progeny. The official position of the SV is that considerable breeding progress in the area of declining HD incidence can be had by implementing measure.

The HD program of the SV

Success speaks for itself. The SV has had a protcol for HD control since 1966, which was recognized at an international technical convention in 1974 as “the best in the world”, Northing has changed about it until recently.

Through mid – 1999, over 260,000 German shepherd dogs had been X- rayed in the SV’s HD scheme, and about 240,000 dogs received that coveted “a” stamp, which denotes official permission for the dog to be bred. Approximately 13,000 new “a” stamps are awarded annually. The percentage of dogs with medium and serve HD was drastically reduced by initially 27%, until today there are only around 6% as identified in the old diagnostic technique. The SV has indeed made greater strides in lowering the number of severe – HD cases and preventing severely dysplastic dogs from breeding, than have U.S. or many other counterparts, and this is to be admired. However, because of the failings in their “standard” diagnostic method (see my articles in the internet on the failings in their “standard” diagnostic method (see my articles in the internet on the PennHIP and OFA methods) the SV has not made as much progress as they shoild have in reducing the number of “carriers” and actual dysplastic dogs that slip through the net designed to catch them. This is why the SV has decided to use Breed Value. What they really ought to do is use both ZW and PennHIP. I am sure you noticed the proximity of those numbers of total dogs rediographed and those “passed”. This should create even more questions about how stringent the “a” stamp program is. It is time to raise the bar, since the SV has reached a plateau just as the OFA - type evaluation has, although with the ZW, that SV plateau will prove to be at a slightly higher altitude.