[Jacob-list] Answer about a white lamb

[Chovhani]

Forgive me, but isn't this perfect example of the benefits of registering
all Jacob's, even the flawed ones, so we can keep track of genes? If there
are too many objections to recording Jacobs as they are (rather than as we
would like them to be), why not a separate class for "imperfects" just to
keep track?
Melanie

http://earthhome.tripod.com - Family & Home - NEW UPDATES!
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"I'm not having a mid-life crisis, I've always been this messed up."
----- Original Message -----
From: <Jacobflock at aol.com>
To: <hettick.1 at osu.edu>; <jacob-list at jacobsheep.com>
Sent: Monday, April 17, 2000 8:10 PM
Subject: [Jacob-list] Answer about a white lamb


Fred Horak substituting for Joan who is out of town and isn't on the
machine!

The questions in this post about an all white lamb:  The post asks (1) what
about the purity? (2) is it a sign of cross breeding? (3) All are JSBA
registered..if JSC would white disqualify one or both his parents?

Might it make sense to rearrange some questions to get to the genotype?

(1) Genotype questions first.  Let's look at the White lamb...Any black at
all..nose, hooves, horns, spotted tongue, nape, eye ring like eye
liner....etc. evidence of the presence of a recessive ss piebald gene.  All
you need is a BLACK spot to "suggest" it is DOMINANT BLACK, and recessive
ss.
 The last places for black to remain before disappearing is nape of the
neck,
a miscule eye ring or face spot.

Look at the parents and the percent white for the sire and dam,  then look
at
the percent white for the sire's sire and dam... and the dam's sire and
dam...and then go back one more generation so you have the lamb back to
great
grand parents. The benefit of registration is the pedigree information.
Next
calculate an inbreeding cofficient for the lamb, then the sire and dam.  IF
the lamb or sire or dam's coefficient of inbreeding is greater than 10%
perhaps even approaching 15%, the culprit is probably inbreeding (it brings
out the best and the wurst).

If the coefficient for the lamb or its parents is not greater than, say, 5%,
see if you can find siblings with complementary (not to be confused with
complimentary) distorted color ratios.  Very often the amount of white and
black is reversed between sets of lambs...one twin might be 90% black, the
other 10% black...opposite looking "twins".  Since these are registered
there
should be a clue in the closet unless only the one complimentary "twin" (not
the wurst) was registered.

Just recently I had an opportunity to see a 95% white lamb with 95 % parents
and each of the three had coefficients between 10 and 16%.  The inbreeding
"fixed" the extreme white piebald recessive.  The question long term is how
to breed out of the extreme white piebald.  One way, if you are confident of
the genotype of the current lamb's sire and dam, is to breed each to a dark
piebald.  The expected result for the first generation is 50-50 and each of
them could produce an extreme white or dark piebald.

The various s (piebald) alleles are heterozygous and are very complex.  You
can selectively breed toward white or black but through the various breeding
generatons the breeder will see a lot of variation.  Remeber it is the
piebald s that makes the dominant black (Ed) have spots.  Culling extremely
(white or black) marked single offspring takes the apparent culprit out of
the gene pool but the parents are the carriers.  The worst scenario is
culling an extremely marked twin and placing the normal colored into
production...it probably carries the problem forward with a 50-50 chance of
expression in the next generation.

(2) Hard questions next.  Lamb, dam or sire highly inbred? Yes, switch dam
and sire.  Get out of the inbreeding loop.  Not inbred?  Send it in anyway
as
a record of the parents progeny not for purposes of registration for
breeding
purposes.  Can you repeat the breeding...time issue?  The record of
subsequent progeny may help verify the genotype of the sire and dam.    The
registration of the dam and sire is an accomplished fact. Virtually no
registry for any breed (or species?) has a mechanism to "unregister" stock
save the Cotswold(?).

Now, with the white lamb (which does not meet the Breed Std.) the breeder
has
to make a judgement as to how to proceed.  If not inbred, why is the white
thus expressed?  Switch ram and ewe to a different ewe and ram.  If at some
point the extreme white piebald reappears, you should have the suspect
carrier.  The suspect carrier should be dropped from breeding ...and any
relatives producing extreme white.  Can you borrow a ram or another ewe and
experiment?

(3) The first question on "purity" or "cross bred", when looking at
registered animals with known pedigrees, is generally the last test
question.
 When buying livestock of any breed, you have to trust the ethics of the
seller (1) see the whole flock (2) sire and dam (3) brothers and sisters and
(4) the family tree.  If "impure" or "crossbred" it will show up or there
will be "unknowns" in the pedigree.




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