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Hip
Dysplasia Latest News |
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A research study funded by
Morris Animal Foundation with grants from The Seeing Eye, Inc. and the Golden
Retriever Club of
In the hip-extended view, the measure of observable laxity was made
using the Norberg Angle (NA), and in the view with
the femoral heads levered out from the sockets as far as they will go, the
measure used is the distraction Index (DI) developed by PennHIP
for early and accurate detection of that most important HD risk factor. The
study was to determine heritability estimates for the different types of hip
scores in this breed. Heritability is a ratio that refers to how much effect
"selection pressure" (choices of breeding partners, mostly) has on
genetic progress; it is expressed by a number between zero and one (0 - 1). The
higher the number, the faster one can make progress (in reducing HD, for
example). These heritability numbers vary considerably from one diagnostic
technique to another.
The heritability estimate of the subjective hip-extended scoring
method was 0.22 and this was not statistically different from zero (0).
Remember, when we use the word "statistically" we are talking about a
specific mathematical science, not the very loose use of such words by the
general public. The heritability estimate for the only objective part of the
hip-extended view (NA) was 0.46, a big improvement. Both it and the 0.64
heritability estimate of the DI method are statistically significant.
Conclusions: Using DI, genetic change (progress in your hip
improvement program) will occur 40% faster than you would expect using the NA,
and a whopping 290% faster than by using the OFA-type hip-extended subjective method.
Further calculations and comparisons showed that the square roots of these
heritability estimates are important: the subjective hip-extended figure here
is 0.47, which means that if you use just that knowledge to choose breeding
partners, you have no more chance of making a lucky decision (improvement in
hips) than if you had just flipped a coin. The DI square root of 0.8 is twice
as high, and your odds of making a wise move armed with such knowledge are
vastly improved. When you factor in the relatively new and
until now obscured calculation of Breeding Value or Zuchtwert,
you can get even more accuracy and faster progress. The Seeing Eye has
been using BV for years, and the largest breed club in the world, the SV (GSDs) has begun publishing ZW numbers for all breeding
dogs, active or potential. I think when the more sensible leaders of the Golden
club sees these data and conclusions, they will want to implement a BV-ZW
system as well as encourage PennHIP DI use by
breeders.
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Note: Fred Lanting is one
of only two SV conformation judges in North & Central America, and has
judged the breed in more than a dozen countries beyond that. His most recent
international assignments have included
