From: crs@beta.lanl.gov (Charlie Sorsby)
Newsgroups: rec.pets.dogs
Subject: Re: Hip Dyplasia
Date: 12 Sep 92 03:25:19 GMT
Organization: Los Alamos National Laboratory

This is mainly a response to Jim Miller's posts which, if I read
them correctly claim that the only value of OFA certification is as
a "Good Housekeeping Seal of Approval."  Jim cites a dysplasia rate
of one in six for OFA certified parents but doesn't, to my
recollection say where he obtained this number.  He makes various
claims but, in essence he seems to me to be saying that OFA
certification's only value is as a means of charging higher stud
fees to the gullible.

If I've misinterpreted what you said, Jim, I'm sure you'll correct
me as well you should.

Jim is, of course, entitled to his opinion as are we all.  The
following is my view of the matter.  I will cite not odds, no
statistics--only my view of the value of OFA (or similar)
certification of breeding stock.

Is OFA perfect?  Of course not.
Will OFA certification guarantee CHD-free pups?  Of course not.

What good are they then?  Well, in my opinion, until recent posts
described an alternative, they were the only organization that I'd
heard of that was making any effort at all to reduce the incidence
of CHD.  Even though they lack perfection, as do we all, they are a
step in the right direction.

CHD is a complex syndrome and there are no, and are unlikely to be,
any easy answers.  Radiographic examination by trained orthopedists
are, according to my reading, the best way at our disposal *now* to
detect CHD in animals that show no clinical symptoms.  The average
veterinarian is not an orthopedic specialist.  He (or, of course,
she) must be a generalist, able to take care of a variety of
problems in a variety of species.  Can your vet diagnose CHD?
Maybe.  Maybe not.  Radiographs sent to OFA are examined by
specialist.  Each radiograph is examined independently by three
such specialists who *independently* grade the joints.  Those three
independent judgements are then combined to form a concensus
opinion.

Jim claims, as I understood his posts, that the CHD incidence in
pups from OFA certified parents is 1 in 6, the toss of a die he
says.  But he doesn't say what it is in the case of parents who are
OFA certified dysplastic.  Is it 5 in 6?  4?  6?  I don't know.
But common sense and a very limited knowledge of genetics suggests
to me that, as with other polygenic traits such as milk production
in cattle, egg production in chickens, nose in bird dogs, ..., the
better the parents, the better the offspring *on average*.

Milk production in cattle is, as is HD in dogs, a polygenic trait.
It is not the simple yes/no of Mendelian genetics.  It is not a
case where a specimen either has it or has not.  It is a virtual
continuum from the ideal of complete absence of the problem to
total presence with the bulk of specimens somewhere between the
extremes.  Cattle breeders have managed to produce animals with
milk production that would, perhaps, have been beyond belief before
they started.  If, with the same kind of trait, they could
materially increase average milk production, why should we not be
able to materially decrease the incidence of CHD in our breeds?

Shall we ignore one of the few tools at our disposal because it is
imperfect?  Shall we allow the incidence of CHD in our favorite
breed to remain in double-digit percentages because OFA (or other)
certification is not a guarantee?  Each of us must reach our own
decision, of course, but I, for one, would rather have an imperfect
tool than no tool at all.

Well, it's past my bed time--5:00 comes awfully soon....


-- 
Best,

Charlie "Older than dirt" Sorsby				"I'm the NRA!"
	  crs@lanl.gov