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Breeding
Programs and Rates of Progress |
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THE
SITUATION TODAY: SLOW PROGRESS AND WHY
Why, after nearly some four
decades of awareness, breeding changes, and study, do we continue to hear from
disgruntled or dissatisfied dog buyers and breeders? Knowing that orthopedic disorders are almost all genetic, one might
think that it would be a simple answer to just breed non-carriers of HD or ED
(elbow disorders), or those with the best genetic bank for good joints, but it
is discovering these dogs that is the challenge. I should address elbows
in a separate article, but shall discourse on hips herein. Now that we have
good diagnostic tools and effective hip registries, the next step toward
progress is for each breeder to develop a breeding program. Fortunately, some
breed clubs and other organizations have already done the greater part of
laying a foundation. We have already potentially removed one of the two major
obstacles to progress, lack of understanding — or in other words, a lack of
good diagnostic guidance. After decades of using the hip-extended method, most
or all of those agencies have not generated a reliable heritability figure for
hip phenotype, nor has the method used in
The other reason for spotty,
slow, or inconclusive progress in reducing and ultimately eliminating canine HD
is non-compliance: the failure of most breeders to stick with a really vigorous
program of control and reduction. As you
might think, some breeders do their best to provide an environment that causes
the least dysplasia.
However, genes that induce HD will thus be masked and therefore retained
in the stock. Few breeders are likely to
provide knowingly the adverse eugenics environment that would reveal such
genes. Part of that second reason (breeding practices) for slow progress is the
win-at-all-costs attitude maintained by many of the more prolific breeders and
leaders of breed clubs. One of my
correspondents, a friend and a widely respected veterinary researcher, wrote,
“Many of the breeding [genetic] defects do not hit the breeder in the
pocketbook and winning in the show ring is all that’s important.” (personal
correspondence with J.W. Bardens, 1986) This neglect is why the Select class of the
annual German Shepherd Dog Club of America National Specialty Show, consisting
of the top 20% or so in that class (on that day) has seen a quality decline,
both orthopedically and in other areas of
soundness. From 1983 through 1991, the
Select dogs (males) that had an OFA hip certificate dropped from 78% to 31%;
the Select bitches fell from 44% to 7% in the same period. Later statistics are
no better. You are hard pressed to find AOE (Award of Excellence) dogs among
the GSDs of the GSDC-America; these are dogs that not
only have placed very high at the National and have a rudimentary obedience
degree, but also are certified normal in hips and elbows.
In some parts of the world,
organizations and individuals have made greater strides than those in
Recently, I received a request
for advice and counsel from a breeder in
There are two likely reasons for
the two different readings, and I suspect both are involved, even though the
bitch has no clinical signs. One is the inaccuracy of the supine, legs-extended
procedure used in diagnosis in
PROGRESS IN THE
Before getting back to the penal
colonies and
The BVA system concerns nine
features, but for practical purposes, only a couple are really important, those
being subluxation and Norberg
angle (these two identifying laxity) and all others put together as a
description of degenerative changes. Values of zero (no irregularities) to 6
(horrible) are given to both left and right hips joints, and the columns added.
The totals are reported in terms such as 3/5, 0/0, 21/18, etc. Adding both
column totals together and coming up with a 20 or higher would stop most people
from breeding such a dog, and most good breeders refuse to use any dog with a
grand total of anything more than 10.
Currently, radiographs of dogs
in the
Besides giving a quantitative
score, the BVA/GSDL scheme also has another important advantage for breeders
over the American OFA and some other systems: it does produce information on
progeny for several breeds. Computer-retrievable data by kennel name, sex, birthdate, age at time of radiography, and numerical value
for each hip are used for genetic analyses and for your own conclusions on with
whom to breed Schatzie, or whether to breed at all in
deference to waiting to buy a better dog.
Say you like the looks of that dog that placed in the Top Ten at his
breed’s national specialty show the past two or three years. You look up his
published hip scores, the mean score of his offspring who are old enough to be
assessed, and scan the column that tells you whether and by how much he
improved on the hip scores of bitches he previously bred. If your breed club doesn’t have that
information, and it’s likely it doesn’t, then it isn’t
doing all it can to serve you and your breed. That’s where “politics” can have
a rare, beneficial effect on purebred dogs and the sport. Get into or start a
movement to require your national club to hire a geneticist and give
instructions to set up a scheme similar to that now employed by BVA/GSDL. Yes,
you can go it alone, but your choices of breeding animals will be more limited
than if you were backed with the power of a club like the
However, despite the UK’s German
Shepherd Dog clubs, through the GSDLeague, being responsible
for developing one of the most advanced information and control schemes in the
world, the mean scores for GSD males and females born since 1959 have not
changed a whit. About 45% of the
Examples of progeny data are
often seen in tables published in breed magazines in the
The “change over dams” column
represents valuable information when colored by other
data. Dogs with a large minus figure
here have sired animals with that much lower (better) mean hip score than the
dams had. Of course, a good male bred
only to 0/0 bitches will show a plus sign here since the offspring will not be
as good as their dams, but if the mean score is low, the “change over dams”
information diminishes a little in importance.
A dog bred to high-score (high HD risk) bitches would show a high minus
value, but the progeny scores will not be as good. As such a scheme with its published data
becomes more used, there will be fewer stud owners willing to tarnish their
dogs’ reputations by agreeing to breed to a poor-producing bitch or one that
has less desirable hips herself, and fewer breeders willing to overlook orthopedic soundness in favor of
one or two flashy characteristics in a stud dog. A similar thing is happening
in
While many breeds have entered
into the BVA/GSDL scheme in
PROGRESS IN
I was an honored guest and minor judging
participant at
According to an issue of the Australian GSD club’s newsletter,
almost all of the Normals (in their breed) and 61.4%
of the Near-Normals score 0-5; the other 38.3% NNs score 6-10, along with 75% of all the A grades. Some 56% of the Borderlines (BL) scored 6-10,
but 40.8% score 11-15. Most of the grade
IIIs score from 11-20. The use of the Willis
statistics as breeding aids have attracted the notice of other breed people in
Australasia as well, so more dogs there will benefit from the emphasis on hip
radiography, open records, and progeny testing in the future. Already, several
of the working, herding, and sporting breed clubs are beginning to participate.
In quality of type,
While hip quality has not
increased as dramatically as quality of type, there are hip requirements
for breeding and, in time, increased strictures will produce faster improvement. Figures for the distribution of hip
evaluations in German Shepherd Dogs in
New Zealand, a two-island
country the size of California but with far lower population, also participates
in the BVA scheme, with radiographs read by a panel of six or eight “scrutineers”.
Between 300 and 400 films a year are sent to the panel head, who
forwards them to the panel in batches of 20, thence to such as Professor Norman
Williamson, then head of the Department of Clinical Sciences at the veterinary
school in Palmerston-North, and readings with
pedigree and other information are sent to Dr. Willis in England. Many
JAPAN
In the modern, dog-loving
portion of
AMERICA
The oldest hip registry is the Orthopedic Foundation for Animals, but there are others,
most notably GDC and PennHIP. It’s a good thing that
OFA requires a minimum age of 24 months for certification of “normalcy”;
otherwise the situation in most breeds in the
Compare progress in the
SV data show not only an
increase in the number of submittals for evaluation corresponding to increases
in both population and breeder/fancier involvement, but also a gradual increase
in number and proportion of “a”-stamp Normals. Concurrently, we see a slight increase in the
“near-normals” at the expense of the mildly dysplastic but “still permissible” (noch
zugelassen) population. Clearly the SV’s
program has shifted the percentages toward the better side of the table. Even faster progress could have been made by
the SV if they awarded the “a” stamp only to dogs radiographed
after 18 or 24 months of age. And in other countries we could see an increase
in the progress rates if all dogs were to be radiographed
and evaluated, even if they had poor hips and would never be bred. It would
give valuable data for progeny testing — find out which dogs are producing
those whose hips were expected to fail and thus were not entered into the
evaluation scheme.
Later Improvements
Two movements in
Can progress be satisfactory
when using an approach that utilizes exclusively the hip-extended position? Yes
and no. As is the case in any subjective method, and analogous to the
differences between artists, much depends on the skill and standards of the
individual. The
Dr. Eldin
Leighton, geneticist at The Seeing Eye, Inc.®
was in large part responsible for that east-coast guide dog school’s notable
genetic progress since 1979, in which the incidence in their breeding program
dropped from 59% to 24% — again, using the leg-extended position. However, the
big difference in this independent investigation was that they also utilized
calculated breeding values (BV), which is the scientific, statistical side of
progeny testing (the Germans call it Zuchtwert).
Most breeders, in contrast, use mass selection based only on phenotypes of the
individual prospective breeding partners. Leighton later added the PennHIP protocol and got even faster progress. Another
important factor in the progress rate with the standard AVMA position at The
Seeing Eye was the use of Dr. Darryl Biery, a
board-certified radiologist who had been known to interpret hip radiographs
more strictly than the OFA did. The combination of these factors yielded real
progress in the controlled population of Seeing Eye candidates and breeding
stock. Further, it demonstrated that even a subjective hip score could be used
to bring about genetic improvement. Not as good as an objective method such as
distraction index, but progress nevertheless. This need for more rapid and sure
progress is why Dr. Leighton said, “To make further progress toward eliminating
CHD, a measure of hip quality that will allow us to distinguish among the dogs
currently in the breeding program is needed. For this reason, The Seeing Eye,
Inc. has turned to the distraction index (PennHIP) as
a means of assessing hip quality”.
USE THE BEST TOOLS
As you have already discovered, the major reasons for lack
of further progress in decreasing HD incidence in a colony or breed, or the
purebred dog population overall, are non-participation (not screening partners
with radiography) and not using the best tools. The bar has been raised, to
borrow a sports (high-jumping) term. No longer is it sufficient to rely on the
old OFA or BVA or Australian or
Breed Value
The ZW (Zuchtwert, which is German for Breed Value) is a number
that reflects a rough estimate of the likelihood of producing good hips. It is
an average of the sire and the dam’s ZW, weighted toward the number of progeny
each has, and which have been evaluated. It has been used for
several years by such clubs as the Jagdterrier and Hovawart groups in Europe, has more recently been adopted
by the SV, and has been used for many years by The Seeing Eye® guide dog school
in the
Compression/Distraction
Stress Radiographic Technique
Although it has been said that
x-raying dogs in the standard ventrodorsal position
“can reveal abnormalities that cannot be detected in other positions”, the
primary indication of HD (or risk of later DJD) is joint laxity; this best can
be revealed in younger dogs by the PennHIP method
employed and promoted by the
At Penn, Dr. Gail
Smith, a veterinary surgeon with an additional PhD in engineering, along with
his radiologist colleague, Dr. Darryl Biery, refined
the concept of the wedge, an earlier form of stress radiography in which force
is used to lever the femoral heads out of the acetabula
if laxity is present. It is variously known as the compression/distraction
method or technique, or by its commercial designation, PennHIP,
which stands for
The PennHIP method is effective in
diagnosing the prime aspect or predictor of HD (laxity) in dogs as young as
four months. Smith once said that he believed his method at four months was 80
percent as accurate as the standard AVMA/OFA diagnosis at twenty-four months.
Later statistics indicate that it is 96% accurate at four months and nearly
100% accurate by six months, when compared to radiographic evaluation done at
twelve months of age. Laxity does not change appreciably over the dog’s
lifetime, especially if the joints are relatively tight to begin with.
Accuracy, however, is not well defined in the context of making genetic change
toward better hips. For that, you need to add the effect of heritability. The
hip phenotype with the highest heritability is one that should be considered
most accurate. And the distraction method has a much higher heritability than
older methods of viewing hips.
The position utilized
in PennHIP is that of a dog that looks like it is standing,
but the picture is upside-down. For a long time I knew that the extended-leg
AVMA standard-view position actually “wound up” the joint capsule, the
ligaments and muscles around the hip socket, when the dog was in that ventro-dorsal mode on its back on the table, but could not
develop a method to get a good radiograph of a standing dog. This AVMA and BVA
supine position thus tends to show a false, temporary tightness of the soft
tissues, often forcing the femoral head more tightly into the socket and making
it look like a deeper seat. The PennHIP method
includes this extended-leg position because that give the best view of most DJD
signs and, if the owner so desires, a copy of this shot can be sent to BVA,
OFA, GDC, etc. for their numbers and the advertising value. For the other two
P-H shots, the vet first seats the heads of the femurs in the acetabula by pressing them in from the “outside”
(laterally), in case the dog has so much laxity that it would show with no
effort. In this way, all comparisons start equally, with heads as fully seated
in the acetabula as possible; in most dogs it
demonstrates the concentricity that is normal and desirable. Then, while still
in the knees-up position and still under anesthesia,
the distraction force is applied medially to push the femurs apart and reveal
latent or otherwise hidden looseness. This force separates the center of the femoral head circle (as superimposed on the
film) from the center of the acetabulum
circle, and the distance is measured with the use of precisely machined steel
circle gauges. A ratio is reported and is called Distraction Index, DI. A threshold level of 0.3 (30% of the way from
no space to 100% out of the socket) is probably the best “feel-good” floor for
the serious breeder, though other aspects must be factored in; examples are
characteristics such as working ability, health, breed type, or temperament.
If, in this distractive view,
there is no appreciable difference from the picture taken with mild
compression, the implication is that the volume of synovial
fluid is normal and that it tends to resist, like a suction cup, the effort to
pull the head out of the acetabulum. If, on the other
hand, there is too much fluid for a stable joint, suction plays a lesser part
and perhaps not until the head is pulled a considerable distance out. The PennHIP compression/distraction technique can discourage
some who have been relying on AVMA false-negative readings, when they see
actual laxity using the PennHIP technique.
The PennHIP
compression/distraction technique might tend to discourage some who have been
relying on the false-negative readings common to the hip-extended view, when
they see actual laxity using the PennHIP technique,
but it is better to face the facts than live in denial. Young dogs with loose
hip joints as shown by this method may not have readily apparent laxity with
other methods and positions. However, as the dog gets older, those that show
greatest laxity with Penn’s method develop obvious laxity with other diagnostic
methods and also show significantly more degenerative
joint disease (arthritic changes). With the PennHIP
method, those dogs with tight joints as young as four
months of age retain tight hips throughout life. Those pups with loose hips at
this age develop a wide range of laxity in later life and a similarly wide
range of osteophytic deposits and changes in shape.
However, as the dog gets older,
those that show greatest laxity with Smith’s method develop obvious laxity with
other diagnostic methods and also show significantly more degenerative joint
disease (arthritic changes). Perhaps the major reason for the higher level of
false negatives (seemingly, but wrongly considered HD-free) in the standard
extended hip ventrodorsal view is that the joint
capsule, which is in its most relaxed state when the dog is standing normally,
is now twisted to its maximum. When you older guys were kids, and wound the
rubber band attached to the model airplane’s propeller, you saw how tightly if
drew the prop against the front of the fuselage and could image that if it
weren’t for the rigid body of the plane, it would draw the ends of that plastic
band closer together. The same thing takes place when the twisting of the
ligaments and muscles around the coxofemoral joint
occurs as you extend the legs almost parallel with the pelvis and the table and
the dog’s spine. This pressure forces the head tighter into the acetabulum; it has to be a substantially lax joint not to
look normal in such a situation.
There are some dogs (usually of
certain giant mastiff-family breeds) that do not develop DJD but are
OFA-assessed as dysplastic because of laxity at two
years’ age. Even more importantly, there is a greater number of dogs of other
breeds that are adjudged “normal” at two years but later develop DJD or produce
an unacceptably high percentage of dysplastic
descendants. Thus, the accuracy of the hip-extended methods is gravely flawed.
Even if reliability (by this is usually meant repeatability of results) is high
from younger ages up to the OFA’s two-year
qualification age for certification or the 12-month stage for other registries,
the absence of accuracy is worrisome to breeders, and diminishes the
importance of published (JAVMA, Nov. 1, 1997) reliability figures. As an
example, Penn cites the OFA-type evaluation of military dogs in a longitudinal
study (JAAHA, 1996) in which all the dogs with normal hips at two years
had mild degenerative changes by nine years of age. At the same time, 22 of 52
dogs judged “positive” for HD at two had similar changes by nine years!
The conclusion is that the hip-extended type evaluation at two years still
gives a relatively high rate of misdiagnosis, and blurs the distinction between
true positives and true negative diagnosis, even at that supposedly “safe” age
of two years. For the breeder, who really wants to know what his dog’s genotype
is, the absence of radiographic signs at two years when using the OFA-type view
is not enough to give confidence in the “true-negative” or “normal”
proclamation or implication that this particular dog is relatively free of the
genetic programming for HD. To a breeder, such false negatives would mean a
severe and expensive setback in his goal to reduce or effectively eliminate HD
in his kennel. The gene pool is hurt most by these false negative diagnoses.
Using the Newer
Procedure to Improve the Breed
It should not be surprising to anyone that the looser the
hips, the less accurate a prediction of a specific grade or severity might be.
HD is developmental (DJD might not show up right away), progressive
(it’ll eventually be worse), and multifactorial
(environment has a part to play in the expression of the bad genes). Some dogs
will get worse than others even with the same DI at a young age. Some breeds
(such as Rottweilers and Saint Bernards)
can tolerate looser hips than a GSD and, with identical DI numbers, have less
arthritic degeneration in maturity. There is very good reason to presume that
dogs that have no early signs of DJD yet have an index higher than the mean for
their breed “represent a carrier state of the disease”, as mentioned in an AJVR
(American Journal of Veterinary Research) report to be found on the websites
mentioned above. In other words, it is a clearer picture of the genotype than
the AVMA view gives. Man has advanced over his prehistoric precedents by using
more tools, and we should progress in use of modern tools regarding HD as we
have from the Neandertal era to the Stone Age to the
Bronze Age to the Machine Age, and to the Computer Age. PennHIP
is such an advanced tool for the serious breeder. The inescapable conclusions
are that:
- Tighter Is better
(agreed on by OFA, PennHIP, and all other
groups);
- Position and technique
(better tools) can discover covert laxity;
- PennHIP
is the best diagnostic-predictive tool currently available.
The pet owner of
course wants a painful, long life for his companion. That is reason enough to
fight the battle against HD and elbow dysplasias, as
well as less prominent genetic disorders. Beyond the pet buyer, there are two
groups of fanciers very interested in improving the average and total hip joint
status in the breed. One group consists of the show and trial enthusiasts who
want to win recognition in competition, enjoy the capabilities of their canine
companions, and appreciate the camaraderie and activity in their hobby. The
other group is composed of the breeders. All three may overlap — you may
consider belonging to more than one category — but one objective is common to
all: we want better dogs with better hips for health, work, and activity over a
long life-span. All three groups can benefit from all three sides of this
triangle of evaluating mature dogs for DJD, using PennHIP
for early risk detection, and following a Breed Value/ZW program. In my
experience, degeneration happens eventually and so regularly that (in some
breeds more than others) the dog owner can say that laxity practically is
dysplasia. The science is sound, the data is
voluminous, the evidence is clear: it is not worth it, in most cases, to breed
dogs with excess laxity. But you must find that laxity in order to make
substantial progress.
PennHIP does not make breeding recommendations, only evaluations; it
leaves the decisions up to you, and counseling up to
your veterinarian and peers. If you get
the PennHIP report and it says your dog is in the 50th
percentile, that means that 50% of its breed have
tighter hips than it does, and 50% are looser. In the 80th
percentile means that your dog’s hips are tighter than about 80% of the dogs in
its breed, and the important lesson you have learned from both OFA-BVA etc. and
PennHIP is that “tighter is better”. You are
perfectly able to decide which dog is better for breeding from the standpoint
of hip joint quality and other characteristics. Naturally, you will want to
breed only those dogs that are in the higher percentiles and have a DI lower
than the mean (since the index increases in proportion to the laxity, smaller
is tighter). In addition, you will be informed by your vet or the Synbiotics website what the current mean (average) DI is
for your breed. The best progress will be seen by selecting the lowest numbers,
or at least those below the mean, and breeding to a dog with a lower DI than
your own dog’s. The higher the DI
number, the greater the risk.
If, as is certainly
indicated, the DI gives a better picture of future hip quality in your dog,
then deductive reasoning would lead you to think of it as a reasonably accurate
indicator of the genotype of your dog. That means a better idea of the
proportion of bad hip genes to good hip genes, which in turn means relatively
how many bad genes are likely to be transmitted to the next generation Now that,
dear friends, is really revolutionary. The lack of further progress we have
seen in modern times, with ratings by BVA, OFA, SV, ADRK, OVC, and other breed
and veterinary organizations is a direct result of their inability to indicate
those hidden genes. A dog that has a good picture in the extended-leg view yet
still produces an unacceptably high number of dysplastic
offspring has too many of those hidden genes. Since OFA would be the first to
tell you of the link between laxity and HD (remember, they actually use that as
a definition), the only reason for the poor progress is the covert laxity I
mentioned earlier. Therefore, using the logical process of thought, if PennHIP shows more of this laxity than shows up in the AVMA
type view, it in effect shows us the effects of more “hip genes”. Since mapping
the dog’s genome (at least finding markers for enough of the polygenic
perpetrators) is decades away, the DI evaluation as promoted by PennHIP is by far the best tool in our tool chest.
