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Date Posted: 11:58:55 03/12/04 Fri
Author: DaVid I.
Subject: Dr. Seltzers comments on Dr. Paggetts. analysis of DKC breed rules

With permission: Dr. Seltzer:
"I thought we had discussed these objections to the DKC breeding
rules some time ago, but perhaps not -- at least not in any detail for I
can find nothing in my archives. It is certainly a subject that merits
some attention.

Repeating the source references:

DKC Breeding Rules:
http://www.canine-genetics.com/dkcbreed.pdf

Padgett's comments:
http://www.nvfr.nl/padgetmemo.html

Willis' comments:
http://www.nvfr.nl/willisInbreed.htm

I suggest everyone familiarize themselves with the DKC breeding
rules prior to reading the comments by Padgett and Willis. The
restrictions on frequency of use of sires is only a part of the DKC
rules, but that seems the major point of dissension.

Padgett's comments can be disposed of fairly quickly since poor
George just doesn't seem to understand the major implications of
inbreeding. As you are aware, Dr. Armstrong tried to educate Padgett on
the subject, but I fear that effort was to no avail.

Padgett writes: "In order for a genetic disease or defect to be
maintained in a breed, the gene or genes involved in the production of
these traits must be distributed in the breeding population of dogs in
that breed. So the genes(s) are present in the best dogs both male and
female in the breed. They are also present in equal numbers in the
non-breeding population, but we never find that out about them because
these animals do not get bred.... So if the Dutch Kennel Club limits
the number of matings which a dog can have, will that prevent the spread
of defective genes? The answer is a clear-cut NO. Every male spreads
defective genes, but it is only with the matadors that we have a chance
to learn what they are. Once we know what the matador carries, we can
use him properly and prevent disease." So Padgett acknowledges that a
matador is just as likely as any other potential sire to carry a subset
of the alleles for hereditary defects that are present in his breed, and
this concession is essential to further discussion.

Padgett's conclusions are based on uncovering the defective genes
carried by a matador by extensive mating to different dams -- sooner or
later a defective pup will be born and we will know that the matador is
a carrier for that particular defect. Once the specific alleles carried
by the matador are known, breeders can avoid doubling up on these by
insuring that their dams do not carry the same defects. However, absent
DNA tests or extensive breeding of the dams to a variety of unrelated
sires, a breeder is unlikely to know what defects a bitch carries.
Perhaps, once a defective pup actually turns up in a litter sired by the
matador, as it sooner or later must, the recommended breeding protocol
suggests that further breeding to the matador be abandoned. But how
about all his get already on the ground, half of which can be presumed
to carry but not manifest the same defect along with many of his
virtues?

IMO, the enhanced ability to simply catalogue the set of defective
genes that a matador carries is not a convincing argument in favor of
widespread use of the dog.

However, there is a counter argument that Padgett doesn't seem to
comprehend, and this argument weighs most heavily not on the first (F1)
but on succeeding generations. This effect obtains when the matador
begins to show up in both the sire's and dam's sides of a pedigree. Let
us assume that the matador, after very heavy use, has been found to
carry the autosomal recessive gene for pupillary dysplasia (a defect
that occurs with an incidence in his breed of only 0.1%). Consider the
incidence of pupillary dysplasia in the future generations of dogs
line-bred on this matador:

COI % Incidence of Pupillary dysplasia %

0 0.1
10 5
20 10
30 15
40 20
50 25

where COI % is the contribution that this matador makes to the total COI
of his descendents.

Of course, one can always assume that once the defect has been
discovered in this breed line, that all further breeding within the line
is discontinued. But that would seem to contradict the primary points
of Padgett's argument: "When breeders find dogs (particularly males)
that produce the offspring they desire, they breed them often. Such
animals are often called matadors because they produce more than their
'fair share' of puppies. They are the best animals in the breed because
they produce what we want."

Willis' comments present arguments that are far more formidable than
those of Padgett. Dissecting his observations is going to take more
effort, and I reserve that task for another day.

Jim Seltzer
Willowind Dalmatians
jseltzer@nbn.net
http://users.nbn.net/~jseltzer

Dr. Seltzer is a phd statitician and dog breeder.

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