[Jacob-list] Answer about a white lamb

[Mary McCracken]

Whew, wonderful!  Thanks.

Reminds me of the train of thought and decisions I made when two purebred
Suffolks produced a spider lamb.  That is recessive and the off spring do
not live to reproduce but there must be many carriers.  Turns up often in
'well bred' show quality animals.  The internet taught me lots on that.  I
knew BOTH ram and ewe were carriers.  I culled the ram!!  Marked the ewe as
a carrier...therefore none of her lambs were kept for breeding just for
market.   Marked her record as a definite Spider Carrier and then marked all
of the ewes that had come from the same seller as possible carriers.  No
lambs were kept for replacement that year and buyers from the previous year
using the same ram but without getting spider expression were notified to
mark their records that they had a potential carrier....50% chance from any
of my ewes and more from the carrier ewe.

Genetics is really fascinating.  I enjoy seeing what my Jacobs produce from
year to year and from animal to animal.

One of last year's wethers is going to become Democrat....he is being
donated to a Democratic fund raiser dinner.  Guest of honor, but not a
speaker.



mary
-----Original Message-----
From: Jacobflock at aol.com <Jacobflock at aol.com>
To: hettick.1 at osu.edu <hettick.1 at osu.edu>; jacob-list at jacobsheep.com
<jacob-list at jacobsheep.com>
Date: Monday, April 17, 2000 5:08 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.
>
>
>
>
>_______________________________________________
>Jacob-list mailing list
>Jacob-list at jacobsheep.com
>http://www.pairlist.net/mailman/listinfo/jacob-list