[Jacob-list] Fiber: black/white/fading/freckles/ticking

[Jacobflock at aol.com]

I recall several posts to the list about ten years ago on this very  
subject; "fading" of black to brown and apparent "turning" black to grey (grey  
not to be confused with 'lilac'). 
 
For the expression of "fading" one might consider the biochemistry of wool  
and the effect of ultraviolet light and diet.  Our eyes sometimes play  
tricks on us; the Jacob is a black sheep with white spots, the Sun (our star)  
does not 'rise' in the east, we turn toward the sun.  While fading is  
noticeable to the naked eye at shearing; dark at the base, lighter at the tip;  
under a microscope (400x) a range of color can be seen along the length of 
the  fiber (dark base to light tip). 
 
"Greying" is a term often used to describe a fiber or group of fibers that  
do not exhibit a contrasted range of color along its length; it appears  
(400x) rather constant along its length and at shearing, often between ages  
of 2-4 years, the black skin seems to be getting lighter.
 
White fiber in the presence of black or faded black fiber may give the  
appearance of fading or greying.  Examination of the fleece sample must be  
done under magnification and removal of the white fiber.  The remaining  faded 
or grey fibers can then be examined in detail.  What is the dark  fiber? The 
magnified look is amazing ... take some fleece to your community  college 
and ask to use their microscope.
 
The black fiber of the Jacob contains eumelanin, a protein formed by  
oxidation of the amino acid tyrosine, a component of the melanin granules formed  
in the wool follicle bulb by cells called melanocytes.  The melanocytes are 
 stimulated by ultraviolet light.  Like water oxidizes iron to produce rust 
 - sunlight oxidizes tyrosine to produce the black keratin  fiber pigment.  
It is through oxidation that eumelanin is produced by  tyrosine.  The 
density of the eumelanin can be observed under a  micrscope.  
 
Melanins binds to a variety of compounds and metals.  Iron tends to  
neutralize the anti-oxidant property of eumelanin but copper tends to strengthen  
it.  Thus a diet richer in iron tends to promote fading, copper reduces  
fading and promotes the structure of eumelanin.  Water, soils, mineral,  forage 
etc in the environment richer in copper would tend to fix the black color  
and reduce fading from UV rays.  Is it possible that there is some  
measurable difference in the breeders environment (water test, soil test, feed  
test) that might indicate copper is richer or poorer (like selenium  measures).  
Some data might be available from soil tests, hay tests, and  water review 
boards that would suggest local environmental conditions.   Might MI be a 
copper rich environment?
 
While sun oxides the tyrosine it also can lead to eumelanin  degradation.  
At a wave length of 320-400 nanometers the ultraviolet light  penetrates 
deeply and triggers the production of oxygen radicals that can harm  molecules, 
protein and DNA  (we get melanoma).  At wave lengths from  290-320 the 
penetration is not as deep but is actually more damaging of cell  structure.  It 
is in the 290-320 range that tyrosine (building block of  eumelanin) 
absorbs UV.  Eumelanin has strong anti-oxident properties and  soaks up the 
destructive oxygen radicals that damage cells.  The tips are  damaged (fade) but 
the base retains eumelanin.
 
Wool also has lanolin which reflects UV rays ... and collects dirt and  
dust which also "discolors" the white and reduces the expected  visual contrast 
between white and black.  The use of coats can reduce  the UV effects but 
cannot completely stop it.
 
A black/white Jacob may be grey as a result of a "greying" gene; a  Jacob 
color locus A which acts only in conjunction with the Black locus. Awh is  
white and dominant to Black (eumelanin).  Awh stops eumelanin production at  
B. The S locus, s for recessive piebald controls the amount of Awhite.  The  
other A loci are Ag (grey) and Aw (wild coat).  Greying may also occur as  
consequence of degradation of the melanocytes producing eumelanin.  Is  there 
any connection between greying fiber and other "black" fiber areas?   Is 
there a connection between shearing dates (March vs. June) and greying?
 
Some greying may be the result of "freckling"; some skin freckles produce  
black fibers other do not.  Generally, freckles that produce white fiber  
are the result of UV rays.  Freckles from UV rays may have a concentration  
along the back.  Freckles in the lamb coat might be considered expressions  of 
the dominant Black with incomplete closure of the spotting gene.
 
Ticking is a dominant gene ... some call them freckles when observed at the 
 first shearing ... but simple freckle it isn't.  Ticking is not  ususally 
observed in the lamb coat; its full effect only appears  with age. Black 
spots appear all over the white areas and grow in number over  the years; they 
can become so numerous and dense that the coat appears  black or grey after 
three or four years.  
 
Fred Horak
 
 
 
 
 
In a message dated 7/11/2010 7:42:41 P.M. Central Daylight Time,  
Hobsickle at aol.com writes:

 
Between Christmas  1999 and New Years I picked up a lilac ram from Laurie 
Foster in  Arkansas.  When I first saw him I thought that I was being shown 
the  wrong sheep because the sheep I was seeing had no visible color 
whatsoever on  his fleece—it looked pure white.  Laurie, assuring me that he was 
just  sun bleached, parted his wool and showed me the lilac color underneath.   
This ram never looked white again here in Michigan. 
-Dan 
 
 
From:  jacob-list-bounces at jacobsheep.com 
[mailto:jacob-list-bounces at jacobsheep.com]  On Behalf Of Linda
Sent: Sunday, July 11, 2010 7:52  PM
To: nlgrose at yadtel.net
Cc:  jacob-list at jacobsheep.com
Subject: Re: [Jacob-list] To keep or not  to keep - my little Jacob sheep

That's interesting. I  have/had very few sheep that don't sunbleach and 
really very few that hold  their color well and fleece is one thing I select 
for (not the only thing, of  course). I have owned few deep black, non 
sunbleaching, non fading, non  graying, sheep with finer fleeces.

For the last two years, I've  purchased fleeces from Gary and Dianne 
Anderson in Michigan. The Hillside  flock has sheep with deep black, 
unsunbleached, soft fleeces. I don't know if  that has to do with the fact that we get 
more sun here in the south or the  fact that the Hillside flock is from lines 
across the country from our  southern sheep. I haven't seen the same color 
retention, non sunbleaching,  fine fleeces in sheep I've purchased from other 
northern flocks.

I'd be  interested in hearing more on this topic from breeders in different 
parts of  the country.

Linda

ROY NEAL GROSE wrote: 
One consideration that you might want to look at is the fineness of the
wool. In our experience, in our flock, the finer wools are the ones that
became brown when exposed to sunlight. This makes some sense...the sun
would discolor the fiber a few mirons deep, and those thicker fibers
would not show evidence of this as readily.
 
Neal Grose
 
  
 
-- 
_Patchwork Farm Jacob Sheep_ (http://www.patchworkfibers.com/)   
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