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Very
few breeders offer a hip guarantee, because only part of the problem is
inherited, the rest is acquired.
The SV states on their own
site that HD is 30% inherited, 70% acquired.
An excellent tool for breeders in the fight
against canine hip dysplasia (CHD), the SV's HD Zuchtwert, or Breed value
assessment number (HD ZW) can give great insight on the
quality of hips that a dog, or her lineage, will
contribute into the progeny she produces. The HD ZW number is an
estimation of the probability that a dog will produce
progeny with CHD.
The HD ZW value factors in
many variables in the calculation, but is based mostly
on the hip status of a dog's progeny. This is the
critical factor in the usefulness of the HD ZW. The
dog's own hip status is only one of several important
variables in the equation, not the sole determinant.
This is because it is possible for a dog with excellent
hip status to produce a majority of progeny with CHD.
And conversely, a dog with Fair hip status can produce a
majority of progeny with excellent hip status. Without
factoring in this critical look at the dog's Genotype
(what his genes pass on to progeny) in addition to his
Phenotype, (what his actual hip status is) real progress
can not be made in reducing the incidence of CHD.
So how does it work? Each
dog registered with the SV is assigned an HD ZW number
at birth, based on its Parents HD ZW numbers. After a
dog is x-rayed, its own hip status is factored into his
HD ZW. Upon producing progeny of his own, the results of
the progeny's x-rays are then factored into the parents
HD ZW numbers. The HD ZW number is not a static value.
It fluctuates depending on what the dog produces! This
is what is important: A dog's Genotype; What the dog
produces. Not his Phenotype; what his actual hip status
is.
An HD ZW value of 100
has been set as the breed average.
HD ZW values LESS than 100 mean the dog produces fewer
progeny with CHD than the breed average. A number
greater than 100 means a dog produces CHD more often
than the breed average.
So HD ZW values less than 100
are desirable. HOWEVER, the focus must still be on
the Total Dog.
Breeding decisions need to include much more than only a
dog's HD ZW!
Working ability and Temperament are most important!
To allow for this, the SV
requires that the calculated HD ZW for progeny of a
desired mating be 100 or less. So a bitch with an HD ZW
of 80 can be bred to a male with an HD ZW number as high
as 120! The pups of a breeding like this would be
assigned HD ZW values of 100 at birth. So HD ZW values
Less than 100 are not just desirable, they offer greater
options in breeding partners. Additionally, stud dog
owners can prove their dog's prepotency by accepting
breedings to bitches with high HD ZW values.
For breeders in the US, you
must register your dog with the SV or USA/SV, and have
the dog's x-ray evaluated by the SV for 'a' stamp. This
also settles the Penn HIP vs. OFA vs. 'a' stamp
question. The diagnostic method to determine a dog's hip
status is not relevant. The most relevant data comes
from a dog's actual production, "Do his progeny have CHD
or not."
There are several sources to
obtain data on an individual dog's HD ZW value. The SV
website has a search engine which allows entering a
dog's SV registration number, or parts of the dogs name,
to obtain the HD ZW. You can also buy the data on CD
from the SV as a one time purchase, or as a subscription
updated quarterly.
This tool is a must have for
every serious breeder! And now, every puppy buyer can
have additional, useful information, regarding the
potential for a puppy to develop CHD.
Breed Value Assessment HD: What is it?
The right answers to the most prevalent questions.
"Where can I take my dog to have his breed value
assessed?" , or "Which Breed Value is better,
over 100 or under 100?" These are the questions about
the Breed Value Assessment HD, that are
put to the Head Office time and again.
That's why the SV has again compiled the most frequently
made queries and Herr
Dr. Beuing, the administrator of the project, answers
them for you.
1. How is the Breed Value HD worked out for my dog? What
is the formula for it?
There is no precise formular in these calculations. The
Breed Value of every animal is considered
"unknown" at the beginning of the calculations. Then an
equation is put up for every animal, of the
formular:
HD = the breed average + Breed Value of this animal +
variation of sex + other influences.
In this equation the breed average, breed value and the
effect of the sex are formulated as the
"cause" of HD. In the SV, 450,000 equations are
formulated for 450,000 animals, with the 450,000
unknown Breed Values. Then some supplementary conditions
(stipulations or prerequisites) of the
laws of inheritance and heredity are mathematically
formulated. Following this, the computer has to
solve the 450,000 equations with the 450,000 unknown
factors. The answers are the assessed
(estimated) Breed Values. This means that there is no
formular, in which a dog's breed value is
worked out on its own.
2. What role does its own HD score play in my dog's HD
Breed Value?
The dog's own HD grade modifies that, which was already
known about the line (sire and dam).
Siblings, (same father and same mother) may differ
through their own HD status. If an animal has
progeny, its own HD status slips more and more into the
background. With 30 - 40 progeny, it is
practically of no consequence.
3. How is a foreign "a" evaluated for the Breed Value
Assessment?
At the this time, dogs from abroad with the "a" are
evaluated in the formulations as though they were
not x-rayed. Their Breed Value Assessment is gained only
through their x rayed relatives. As these
animals can not be clearly termed as "free" or "still
Acceptable", an assumption in this case, would be
unfair.
4. How can a dog, that was not x -rayed, have a Breed
Value for HD?
In the system of equations (see Answer 1), there is a
lateral clause, that the father (and the mother)
give half of their genes to the progeny. Therefore the
Breed Value of the progeny can be assessed or
estimated, if nothing is known about the animal ( un
x-rayed), as well as the breed value of the sire
and dam are known. In the same way, a parent can be
assessed if the progeny is known, because
progeny have one half of their genes from their parents.
Siblings on the one hand help to
characterise the parents, the knowledge about the breed
value of the parents helps on the other
hand, to assess the breed value of the untested
siblings.
5. How accurate can the Breed Value Assessment be, if
for more than half of the whelps, no
HD information is available?
In the Breed Value Assessment, the percentage of the
pups does not matter, but the absolute
number. The last Sieger has at this point in time, 91
x-rayed progeny, who characterise his heredity
well. In the breed Value Assessment it is not the
percentage of the whelps that counts, but the total
number! The last Sieger, at this point in time, has his
heritage well demonstrated by 91 progeny.
6. My bitch has passed on the "a" well up to now. What
happens if I mate her to a dog that has
a HD Breed Value over 100?
If the bitch has produced well, this must be seen in her
Breed Value. Good progeny however, can
also be the result of good matings. If the bitch, for
instance, is mated to a dog with a value of 100,
then the risk for the puppies is higher. The bitch is
only "accredited negatively" if the pups are worse
than could be expected with that dog.
Generally it is a fact that the stud dog owner would be
well advised if he also accepted "poor"
bitches, because with the poor bitches a dog can show
plainly that he "improves"
With HD, where there is no freer than free, it is
difficult to prove a positive heritability of the top
bitches.
7. How do dogs that have no HD findings flow into the HD
Breed Value calculations?
At this stage un-x rayed animals are neutral for the
Breed Value Assessment, they are not taken into
consideration.
8. What does the mean Breed Value of 100 mean, and the
stated deviation of the standard of
ten points mentioned in the breeding plan?
The Breed Value of 100 means, that the animal's heredity
is typical for the breed. At this time the
breed mean is 1,71, that is between HD free and slight
HD. What is passed on, can be better or
worse than 100.The average deviation above or below
this, will be set at 10 points for the mean.
9. What does a Breed Value over 100 mean for my dog?
The Breed Value for one's own dog means that he passes
on poorly. As the breed average itself is
still unsatisfactory, matings should be strived for that
lie under 100. With this, "you must not throw
out the baby with the bath water."
The first priority is working
ability, Temperament and so on. If one
finds a stud dog who brings the expectations for the
pups (the average of father and mother) below
the 100 value, that is sufficient.
10. Conversely, what does a breed value below 100 mean
for my dog?
A Breed Value below 100 means, that there is a greater
freedom in the choice of dogs firm in
character, strong in performance and of good
construction, even if their breed value is around 100.
With a bitch value of 83, one can even accept a dog of
117!
11. Can a Breed Value be worked out for criteria other
than HD, and if yes, for which ones?
A breed value Assessment can be taken for other
characteristics. For this, it is important, that the
characteristic is accurately defined. The inheritance of
size, it is thought, will be described next.
These breed values would then be purely for the
breeders' information in their breeding plans. There
will be no editions published for this.
Dr. Reiner Beuing
University of Gieen
Informational Links:
Verein fr Deutsche Schferhunde
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