[Jacob-list] Early greying

[dave & katrina]

Hi Fred and list-
So just curious...do you think that these same statisics apply to sheep
which gray at 3 and 4?  Katrina

----- Original Message -----
From: <Jacobflock at aol.com>
To: <humbug7 at worldnet.att.net>; <jacob-list at jacobsheep.com>
Sent: Monday, June 11, 2001 4:19 PM
Subject: [Jacob-list] Early greying


> Grey haired Fred Horak here.  These are neat observations on grey sheep
and
> non-grey sheep.  I ask indulgence on adding to this observation with three
> messages: the "greying" gene is dominant, the Ticking gene is similar, the
> observations reveals the sire and dam genotypes, observations of this
nature
> are important for the breeder and breed.
>
> If you have a Jacob that tends to grey at one to two years of age, whether
> ram or ewe...either ram or ewe...and suppose they are bred (thats the
reason
> I changed from "whether" ram to "either" ram..), the phenotype you see
(the
> early greying gene G), must be in the genotype at least as a Gg
> (heterozygous) but may be a (homozygous) GG.  The non-grey is a recessive
gg.
>
> Because it is dominant you see it whether the genotype is Gg or GG.  One
can
> change the genotype of the Jacob by purposely using and promoting the
greying
> (spinners may like this) or by accident (the use of a Gg or GG ram lamb
over
> the flock and producing a crop of Gg and GG Jacobs).
>
> If you wish to get rid of the premature graying before the trait is
"fixed"
> in the flock or the breed (the whole  flock and breed become GG), steps
would
> have to be taken to retain  the Gg or conserve the recessive gg.
>
> Using heterozygous parents, the chances of retaining the Gg is 1/2 and the
> chances for conserving the "non-graying" homozygous gg is 1/4 (GG, 2Gg,
gg).
> Chances improve for non-greys to 1/2 for a Gg to a gg (2Gg, 2gg).   The
odds
> are on our side that there will be a ram and ewe with the recessive
> non-greying gene; i.e., heterozygous.  However, "fixing the greying trait"
is
> also possible by purposeful selection or not being aware; you can not get
a
> non-grey from a flock or breed of homozygous (GG) gray Jacobs.
>
> Ticking is the appearance of spots over time from areas that were clear in
> the birth lamb fleece.  The "freckles" that appear from nowhere is
Ticking.
> The Ticking gene and Graying gene are dominant and operate in a similar
> manner.  You can substitute T's for G's for the two phenotypes and three
> geneotypes.
>
> The observation of early graying and and observations of ticking in
parents
> and the progeny ratios (as described in the other posts) is the evidence
of
> the genotype of the sire and dam.
>
> The "breed" questions then follow...should the Breed Standard for the
Jacob
> be changed to include the dominant greying genotype?  (ala the recessive
> "lilac")... or does one wait until the genotype is expressed before
> registering (ala appearance of true horns vs. aberrant horns or scurs in
> ewes) ..or add longitudinal registry data to reflect these changes over
> time?...or does it even matter?
>
> The practical "breeder" question might be...Do I breed lambs at 6 months
that
> have not yet revealed their phenotype/genotype... or breed unaware of the
> parents genotype (phenotype  and pedigree information)?...or just ignore
the
> question because of my environment (space, time, cost) ?
>
> Wandering mind question: Are birth freckles recessive?...By birth freckles
I
> mean the little "pencil eraser head" spots present in the brith fleece (as
> opposed to ticking); the incomplete closure of the recessive piebald on
the
> dominant black.  Ticking and freckles can be present in the same dermis.
> Does one get "birth freckles" from clear parents?  Are Ticking and Birth
> Freckles linked?
>
> Some breeders want to buy "a homozygous Jacob" lamb that doesn't grey,
> doesn't have birth freckles, doesn't get freckles, with four perfectly
> balanced and separated horns and a 'primitive" look'", four inch fleece,
> crimped, micron with minimal deviation, low mangement and attendent
protein
> demand, good mothering, only produces twin ewes, parasite tolerant,
disease
> resistant, etc.... The Jacob, first known as the Spanish sheep with four
> horns, brings to mind the Spaniard Don Quixote and the "Jacob Breeder"
song
> from Man From LaMancha....download "The Impossible Dream" from Napster.
>
> Fred
>
>
>
>
>
>
>
>
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