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by Bob-O on 03 November 2010 - 03:11
Sitasmom, if a dog is graded as passing by the S.V. and his ancestors and siblings are unknown, then yes, he is awarded ZW 100. If his ancestors/siblings/progeny are eventually evaluated by the S.V., then his ZW can change for better or worse.
The calculation uses factorials that make it much harder to a dog's ZW to improve - he requires many examined progeny with passing scores of at least "a" fast Normal, and of course "a" Normal does improve his ZW. These factorials make it easy for his ZW to worsen quickly if he produces any level of dysplasie. A dog who normally produces well and can produce but one (1) dysplastic puppy and his ZW can take a serious hit.
That is another value to the ZW - it is not a static number.
Best Regards,
Bob-O
The calculation uses factorials that make it much harder to a dog's ZW to improve - he requires many examined progeny with passing scores of at least "a" fast Normal, and of course "a" Normal does improve his ZW. These factorials make it easy for his ZW to worsen quickly if he produces any level of dysplasie. A dog who normally produces well and can produce but one (1) dysplastic puppy and his ZW can take a serious hit.
That is another value to the ZW - it is not a static number.
Best Regards,
Bob-O
by SitasMom on 03 November 2010 - 04:11
Would all dogs that pass and have no ancestors or siblings on file recieve a ZW 100,
or would dogs with "a1" l hips get better number then an "a2" hips?
From another thread.......
"So according to the SV scheme there is little heredity problem; and furthermore it is advised that any ZW below 75 can be used for improvement in this area."
by Bob-O on 03 November 2010 - 11:11
Sitasmom, as far as I understand the protocol; "a"2 hip rating is considered to be the norm, and of course the value of 100 is the mean. So; would a dog (with unknown ancestry, unknown siblings, unknown progeny) receive a better ZW if he has a"1 hip rating?. I do not think so. How about the same dog with a "a" 3 hip rating? It is still a passing score so the mean ZW should be unaffected . The outcome (ZW changes) is driven by inputs.
So, a dog with unknown ancestry, "a"2 hip rating and a ZW of 100 is bred to a bitch with unknown ancestry, "a"2 hip rating and ZW of 100. If all progeny have "a"2 hips, then the parents' ZW should remain fairly static. If some of the progeny (say 50%) receive a "a"1 hip rating, then the ZW of the dog and the bitch will start dropping slowly as both are "improving". But its takes a lot of passing progeny with "a"1 hip ratings to make a significant improvement to ZW ratings, and progeny with failing ratings can really have a negative impact on the ZW.
The S.V. formula is based upon the ideas of normal distribution. With any breeding pair (that have passing hip ratings) there will be a certain percentage of "a"1, "a"2, "a"3 hip ratings (as well as some failures) shown in the progeny if they produce enough. For there to be a meaningful result there would have to be about one-hundred (100) progeny to prove their true worth! And while that is not impossible it is not the norm for most breeding pairs.
I don't remember the exact percentages of distribution at this moment so I will make an approximation. Let's say that from a breeding pair that have at least "a"2 hip ratings; that 40% of the progeny have "a"1 hip ratings, 45% of the progeny have "a"2 hip ratings, 9% of the progeny have "a"3 hip ratings, and about 6% have the failing hip ratings of "a"4 or "a"5. This distribution is close to the findings for all German Shepherd Dogs who are evaluated by the S.V., and would be considered fairly normal.
If the progeny beat the odds and skew the rules of normal ditribution by having a higher percentage of "a"1 hip ratings than the norm, then the parents' ZW begins to improve a bit one (1) point or two (2) points at a time over a long period of time. But if there are just a couple of litters and a single dysplastic puppy appears, the ZW can increase quickly by perhaps three (3) points or four (4) points in one (1) move! Of course one expects mating pairs with better hip ratings of "a"1 to beat the odds a bit with their progeny. That is what one expects, but the progeny evaluations and ZW fluctuation will be the proof here!
A dog's ZW can continue to make small changes long after his passing if his progeny, their progeny, and so on, are evaluated. That is what is useful about the ZW, as it is never truely static as long as there are successive generations of progeny. As useful as the ZW is; it is but another tool and never a guarantee of the outcome. But at least the S.V. has enough data to apply this system and make it work fairly well. That is where they excel compared to other kennel clubs and hip rating registries.
Best Regards,
Bob-O
So, a dog with unknown ancestry, "a"2 hip rating and a ZW of 100 is bred to a bitch with unknown ancestry, "a"2 hip rating and ZW of 100. If all progeny have "a"2 hips, then the parents' ZW should remain fairly static. If some of the progeny (say 50%) receive a "a"1 hip rating, then the ZW of the dog and the bitch will start dropping slowly as both are "improving". But its takes a lot of passing progeny with "a"1 hip ratings to make a significant improvement to ZW ratings, and progeny with failing ratings can really have a negative impact on the ZW.
The S.V. formula is based upon the ideas of normal distribution. With any breeding pair (that have passing hip ratings) there will be a certain percentage of "a"1, "a"2, "a"3 hip ratings (as well as some failures) shown in the progeny if they produce enough. For there to be a meaningful result there would have to be about one-hundred (100) progeny to prove their true worth! And while that is not impossible it is not the norm for most breeding pairs.
I don't remember the exact percentages of distribution at this moment so I will make an approximation. Let's say that from a breeding pair that have at least "a"2 hip ratings; that 40% of the progeny have "a"1 hip ratings, 45% of the progeny have "a"2 hip ratings, 9% of the progeny have "a"3 hip ratings, and about 6% have the failing hip ratings of "a"4 or "a"5. This distribution is close to the findings for all German Shepherd Dogs who are evaluated by the S.V., and would be considered fairly normal.
If the progeny beat the odds and skew the rules of normal ditribution by having a higher percentage of "a"1 hip ratings than the norm, then the parents' ZW begins to improve a bit one (1) point or two (2) points at a time over a long period of time. But if there are just a couple of litters and a single dysplastic puppy appears, the ZW can increase quickly by perhaps three (3) points or four (4) points in one (1) move! Of course one expects mating pairs with better hip ratings of "a"1 to beat the odds a bit with their progeny. That is what one expects, but the progeny evaluations and ZW fluctuation will be the proof here!
A dog's ZW can continue to make small changes long after his passing if his progeny, their progeny, and so on, are evaluated. That is what is useful about the ZW, as it is never truely static as long as there are successive generations of progeny. As useful as the ZW is; it is but another tool and never a guarantee of the outcome. But at least the S.V. has enough data to apply this system and make it work fairly well. That is where they excel compared to other kennel clubs and hip rating registries.
Best Regards,
Bob-O
by SitasMom on 03 November 2010 - 15:11
from this chart by the OFA, and if we assume that fast normal is similar to "fair" then the probability of generating a dysplastic puppy from to fair 20% - which is similar to the general population of GSD's
the first chart, showed that "fast normal" encompases both "fair" and "borderline". Unfortunately this chart groups borderline, and all the dysplastic catigories togehter.
if breeders are supposed to be improving the breed, then why do people knowingly breed to "fair", "borderline", or "fast normal" with the same?
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