Re: [pyrnet] GPCA -- and dwarfs

[Kshoffman@aol.com]

In a message dated 10/11/2000 10:28:25 AM Eastern Daylight Time, 
JGentzel@aol.com writes:

> From what I read about Dr. Padgett, he is a believer in identifying
> the carriers and using a known carrier in breeding would be one
> method of identifying other carriers. I certainly will not speak for him
> as he does this so elegantly himself and I would recommend anyone
> who wants accurate information to reference his writing as a source.
> Some are on the Internet free and he has a book as well.  I would
> recommend anyone who wants accurate information to reference his
> writing as a source.

First off, let me say I think Dr. Padgett is seemingly a nice guy (I met him 
one), and certainly he is an engaging speaker in the eyes of many.  I know a 
number of breeders come away from his lectures and seminars feeling like they 
learned a lot, so in that sense, much of the work he has done over the years, 
especially with GDC promotion, has been of benefit to dog breeders in a 
number of ways.

I would also recommend getting his book and reading it, but I feel it is 
necessary to point out there *are* opposing opinions and revealing critiques 
from others in research academia (relative to health and genetics and 
purebred dogs) to some of Dr. Padgett's ideas, assertions, models, and 
recommendations, and that these differing opinions should be considered as 
well.

There are a number of credentialed highly respected professionals who feel 
some of Dr. Padgett's ideas don't warrant as much merit as many seem to 
believe they do, and there is also some question as to the *accuracy* of his 
work.  Certainly it should be expected when a work such as Dr. Padgett's book 
is published and so well received by the masses of dog breeders that it will 
be scrutinized, peer-reviewed, and even challenged by credentialed 
professionals, especially in the population genetics and mathematics 
disciplines, neither of which are Dr. Padgett's fields of expertise.

Perhaps some are unaware that Dr. Padgett's book has come under some rather 
intense scrutiny in the academic/research communities for numerous flat-out 
inaccuracies and errors, especially in his application of formulas and his 
computation of mathematical probabilities in some of the models he presents, 
not to mention some of his assertions with regard to how the reduction of 
deleterious allelic frequencies on the population level should best be 
handled.  Again, one school of thought, and there are others.

Dr. Padgett is not formally trained as a population geneticist, nor as a 
mathematician, nor as a statistician.  His background and formal training are 
in veterinary pathology, and out of that training and professional experience 
he has developed a special interest in canine genetics and disease control.  
Nothing whatsoever wrong with that, but I think it is important to note that 
others who have more specific advanced level education, training, and 
research experience in these fields have challenged some of Dr. Padgett's 
work.
 
I myself have Dr. Padgett's book and I think overall it is a piece that fills 
a void in many ways, that it has it's place for dog breeders.  I refer to it 
often with regard to constructing genetic pedigrees, and also relative to 
general usage/application of pedigree risk analysis methods, although I 
accept his risk analysis models with the understanding that many of them are 
not considered to be mathematically accurate by those who make their livings 
setting up mathematic and statistical models and computing formulas and 
analyzing data.  I have the luxury of knowing a Ph.D. mathematician and a 
couple of Ph.D. population geneticists/university professors (both of whom 
also happen to be a dog breeders/fanciers) with whom I can consult with on 
these matters.  I don't tend to go solely by one person's opinion (which may 
be inherently biased) in my decision making process, with regard to ANY 
matters of importance in my life.

I sometimes reference the lists of genetic defects Dr. Padgett has compiled 
by breed although I don't accept his lists to be wholly accurate and all 
inclusive. I simply think we should be careful with regard to viewing and/or 
accepting Dr. Padgett as any kind of authority on population genetics and/or 
mathematic or statistical principles and application.  At least some of what 
he presents in terms of recommendations to breed clubs as a plan to reduce or 
eradicate genetic disease is strictly his opinion, merely one school of 
thought, so his work is clearly subject to debate both by other scientists 
and by breeders.

For example, I have no problem with the idea of test breeding, which he 
covers extensively in his book, but the truth of the matter is, test breeding 
is going to be distasteful to MOST breeders for obvious reasons -- it 
sometimes dictates going into a breeding situation knowing full well one will 
produce sick and/or debilitated animals.  While I don't personally have an 
issue with test breeding, and I probably would be willing to do so myself 
under the right circumstances, either on my own or in conjunction with a 
research team, I have found after three years of participating in several 
all-breed discussion groups, and talking with a number of breeders in various 
breeds, that the majority of dog breeders simply aren't prepared to deal with 
test breeding and its potential consequences.  In other words, I don't 
necessarily find test breeding to be a very practical or realistic solution 
across the board to some of the problems many purebred breeds face, and Dr. 
Padgett seems to place a lot of emphasis on the use of test breeding to 
identify carriers.  Take away that part of his recommended plan to control 
genetic disease, and how effective does his plan become?  Not very, in my 
opinion.

> My only concern earlier was that I felt we might be leaving the
> impression that there "were not Dwarfs produced that disfigure, maim
> or otherwise render an animal nonfunctional (i.e., cataracts, retinal
> dysplasia and  detachment, chondrodystrophy)."

I feel this is at least partly a matter of interpretation.  I have produced a 
single dwarf in my breeding program (as a co-breeder, I bred and co-own the 
dam) and while I certainly won't argue this dwarf is perhaps "disfigured" (in 
comparison to non-dwarf Great Pyrenees) she most certainly is not maimed, nor 
is she nonfunctional.  She is basically in fine health and leading a normal 
life.  *Her* disfigurement is no more so than a basset hound or a corgi or a 
dachshund or a PBGV.  She has been x-rayed from head to toe and had series of 
assays run from blood to evaluate various systemic functions and there is no 
evidence so far of any *debilitating* abnormalities orthopedic or otherwise.  
I would imagine, however, she is at the same risk of spinal injury that many 
purposefully bred chondrodysplastic breeds are due to their structure. That 
said, I don't imagine Dr. Padgett is suggesting all breeds with shortened 
limbs due to genetic growth plate closure abnormalities, and/or at 
comparatively higher risk of spinal injury or deformity should be eliminated 
due to their disfigurement.  I personally must put the issue in this 
perspective, others may choose to put it in whatever perspective they wish.  
This is not in the least to say I find dwarf Great Pyrenees to be "cute", nor 
is it to say I condone the perpetuation of dwarf Great Pyrenees.  It is 
merely to say on my own priority list of genetic defects, those *I* must 
prioritize in my breeding program, dwarfism is probably not going to be at 
the top of my list every time.

As I have stated in the past, I find epilepsy, just for one example, to be a 
much more debilitating condition than dwarfism, and it's highly doubtful 
anyone is going to change my mind about that.  Perhaps it's my bias, so be 
it.  We all have our biases colored by personal experiences. Coming from 
another breed (Belgian Shepherds) with a 15-18% epilepsy affected rate, I am 
very sensitive to *that* issue, and I can't tell you how many pet owners in 
various breeds I've chatted with about epilepsy, listened to their 
heartbreaking stories, and heard their sobs and shared their tears.  Yet, 
I've talked to many owners of dwarf Great Pyrenees who have not even remotely 
expressed anything close to such heartbreak and despair over the health 
condition of their dogs.

I think every breeder has to define their own "hierarchy of disagreeableness" 
as Dr. Padgett calls it.  His suggestions are merely basic guidelines one can 
attempt to follow, sometimes necessarily rearranging priorities as needs 
dictate.  As a matter of fact, he apparently has done just that in his own 
published work.  I notice he has changed his recommended priorities in his 
book from what he apparently at one point recommended in some of his earlier 
lectures.  Perhaps he has changed his mind again and further rearranged his 
suggested priorities since his book was published. Plenty of other 
professionals may well suggest or recommend to breeders that these priorities 
should be rearranged in a slightly different fashion from what Dr. Padgett 
has proposed at various times over the course of several years.

There really is not a simple right or wrong answer as to how we should handle 
some of the issues we face as in our breeds, and I personally feel at this 
point, attempting to dictate or even strongly recommend to all breeders 
precisely what their priorities should be, what they should breed and what 
they shouldn't breed, is not the way to go. It simply encourages many to do 
what they planned on doing anyway but in secrecy out of fear of recrimination 
for their choices. I can nearly assure all if we start placing those types of 
restrictions on what choices any given breeder can make, it WILL NOT be 
conducive to the type of data sharing we all need to avoid breeding dogs 
afflicted with ANY debilitating genetic defect.  The breeder police mentality 
is not the ultimate solution to our problems.

On the subject of breeding carriers, Dr. Jerrold Bell did an interesting 
interview in a recent GDC newsletter addressing the merit behind the 
potential use of carriers in a breed population over a period of time in an 
effort to retain beneficial genetic material while slowly attempting to lower 
allelic frequencies for defects.  Of course, his is just one opinion on that 
topic, but I must say I've had the opportunity to consult with *many* 
scientists, geneticists and veterinary health care professionals, who agree 
with his opinion.  I can post the article to the list or I can send it 
privately if anyone is interested.

Kelley Hoffman
kshoffman@aol.com