Westwood Kennels LLC.
HD Zuchtwert Breed Value Assessment Number:
The best tool for breeders in the
fight against canine hip dysplasia (CHD), to come along in
years, is the SV's HD Zuchtwert, or Breed value assessment
number (HD ZW). 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
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
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 PennHIP 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.
If you wish to check the ZW value for
a specific dog, follow this link to the
John Paver for
the use of this article.
Nancy Rhynard Westwood E & C LLC
Westwood E & C LLC
4355 Langton Road
Hilliard, OH 43026
Phone (614) 876-2296
Fax (614) 876-9812