[Jacob-list] Jacob horns and color

[Jacobflock at aol.com]

In a message dated 10/8/02 9:51:18 AM Central Daylight Time, bandb at in-tch.com 
writes:


> The first is about horns.  We have stranded electric fencing, the NZ high
> tension kind.  Does anyone know if electricity goes through horns or not, 
> or
> do the horns insulate them from getting shocked?  Was wondering if a horned
> sheep would use his horns to push through the electric fence and then if
> shocked would they get tangled in the wires trying to get out?  That could
> be a real mess,...I think.  Another is how fragile are four horned horns?
> We used to have Scottish blackface sheep and we could use their horns for
> handles when moving them about.  Can you do the same with four horned 
> sheep?
> I have also heard that four horned sheep are more careful with their horns
> and don't go bashing them about like a two horned  sheep/ram.  Is this 
> true?
> Do you folks find any difference between the personalities of 2 horned and 
> 4
> horned rams?
> 
> Next questions are related to color.  Some people have written that Jacob
> come in black and white, brown and white, and lilac and white.  Other 
> people
> only mention lilac/white and black/white.  Are there really the three
> colors, or are the brown one just faded blacks?
> Then I was wondering about the genetics of the lilac colors.  In rabbits
> which also have a gray color called "Lilac" the genes are Bb Bb, and Dd Dd,
> or a dilute chocolate gene.  Is this true of the genetic makeup of Lilac
> Jacobs?  If not then what is the makeup?
> 

The horns of the Jacob, wether two or more, are solidly attached to the skull 
by an internal core.  The core carries substantial quantities of blood which 
also acts as a "cooling" system ... like the radiator of a car.  The 
conductance of the horn depends on two factors .. you can also do this 
experiment.  Using a "cattle prod" (most use 4 D batteries) you can touch the 
end of the horn and get no reaction.  As you get lower on the horn, a 
reaction can be induced.  I think (hypothesis) that this is a function of the 
moisture content of the horn and the mass of the horn core vs. the thickness 
of the keratin sheath.  The problem with some electric fencing is not the 
conductivity of the horn but the catching of the horn in the fence, 
subsequent struggle to get loose, getting fouled up in the fencing, and 
constant pulsing of the charge.  As an aside, I understand that some Jacob 
breeders have used the "Premier" portable fencing with some degree of 
success.

The horns are firmly attached to the skull and can be used to handle Jacobs.  
The two horn and four horn have differing basal size and leverage issues.  
There are no "wild" four horn sheep because the four horn is at a 
disadvantage in competition (combat) with a two horn.  We have notice little 
difference in the bashing of two and four horn .. the process is slightly 
different.  The two horn seem to prefer to go head to head - the four horn go 
head to head but also do more head to body.  Is there a "personality" 
difference?  I think there is some difference but I do not think it is merely 
a difference between two and four horn  .. perhaps more a difference in 
management practices.

Color is rather straight forward ... a dominant black with th recessive 
piebald ... a black sheep with white spots (the basic genotype of the Jacob) 
... and not so straight forward ... "it can also be 'lilac'' (a recessive).  

The black color is observed at the base of the fiber ... it should be black.  
The brown at the neds of the fiber can be caused by several agents ... ultra 
violet light at the high range (sometimes referred to as bleaching) .... a 
lack of copper in the diet or a genetic mechanism that does not convert the 
copper to eumelanin (black).  The amount of white is controlled by the 
piebald gene and an "overactive" piebald gene can result in large white areas 
... the Dorset Horn is also a piebald ... and an 'underactive' or weak 
piebald gene can produce large black areas ... the recessive black Hebridean 
which (if cross bred) produces little white areas.  

A black may also turn 'grey' ... a premature grey that might be observed 
about age three ... this is a dominant gene.  A 'black and white' might turn 
to a 'black' as a result of the ticking gene (the appearance of more and more 
'freckles' over time) and this is a dominant gene.  

The lilac is a recessive.   It is not allowed in the Jacob in England for 
pure bred registration purposes ... but is recognized in North America ... 
perhaps this is a 'British' Jacob landrace issue (Soay, Shetland, etc.) and 
what we have (?) in the North American 'gene puddle'.   The lilac MAY BE 
(hypothesis) a 'modifier' set of genes that affects the dominant black at the 
'eye ring' and 'body' ... but does not affect the breed specific black 
markings.  Perhaps the lilac carries a variant at the Extension locus ... or 
... carries a Dilution gene that is recessive to to deep black.

Ah, sweet mysteries of life.  Fred Horak
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.pairlist.net/pipermail/jacob-list/attachments/20021008/73aa7268/attachment.html