[Jacob-list] Gender Linked Horns, Scurs, & Genetic Letter for Lilac

[Jacobflock at aol.com]

The Jacob breeders in North America may have to propose and  prove to 
COGNOSAG or other body that a definition is  warranted inasmuch as the "lilac" 
Jacob is an apparent variety? of the  'true' Jacob, globally defined as a 
dominant black, recessive piebald,  polycerate.  Absent reliable pedigree data 
(source stock) and genetic  testing and some 3rd party review, a definitive 
answer for "lilac" will  remain hostage to speculation.  
 
There are many sex-linked "horn" breeds and, although the Jacob is not  
supposed to have the sex-linked "hornless" allele, the evidence supporting  
incidents of Ho(hl) in Jacob ewes has been around for at least fifteen years 
and  was a consideration in setting up the breed standard.  In fact, I recall  
cases of Ho(hl) were shown at the JSBA meeting in CA.  Think of the Horn  
gene as having four alleles: polled, horns, multiple horns and hornless.   
Horns, inside the outer black sheath, have a unique structure that seends  
blood in and out to a nasal area (a radiator system) to the cavae mirabilis.  

The hornless allele in Jacob ewes expresses three phenotypes  at the 
lateral: the aberrant horn, short scur and long scur.  First, as  some of you 
know, the true horn is integral to the horn structure; the  expression of the 
hornless allele "sits on the skull"  structure, the  material anchoring the 
aberrant horn and short/long scur are obviously not  horn but a plasticized 
keratinous material.  Whereas the  true lateral horn is part of the skull 
structure (frontal and  parietal), the hornless allele does not produce a 
pourous "boney"  structure.  A "test" for an aberrant horn can be  done on the ewe 
 between three and six months (CDT time?) ... if the apparent lateral horn  
breaks off easily, reveals little more than a trickle of blood and reveals 
a  "plasticized" inverted V ... it is an aberrnt horn. Sometimes one may 
find  a broken horn in the loafing shed; pick it up and look inside ... if you 
see a  little inverted V it's probably aberrant ... find the ewe with the 
missing  lateral and look at the side of its head ... there probably will be a 
 little plasticized bump with little evidence of blood.   HORNS  have  a 
pourous blood rich core ... scurs are primarily dense  plasticized keratin 
material.  Just because one sees a "black sheath"  does not mean it is a 
"horn".  Scurs generally appear like a  yellow/brown/grey  polished plastic stub.
 
If you look up more information on horns, look for info that includes  
Montgmery's work (c. 1996) which places the sheep gene on ch10 rather  than 
using the older bovine synteny analysis on ch1 or an  old high school biology 
book. 
 
Fred Horak
 
 
In a message dated 8/5/2010 4:59:51 P.M. Central Daylight Time,  
ranchrat at telusplanet.net writes:


Heel  low: 
Has there been a  genetic letter assigned to Lilac and what is it please?   
I am being  told that other mammals coined “lilac” are recessive brown and 
recessive blue  (b/b d/d genotype), but d (blue) is not found in sheep.   
Help? 
Which breed of  sheep has the sex linked inheritance in horns?   Certainly 
not the Jacob I may presume! 
Am being told that in  this gender linked horn trait for sheep:  “ rams 
show the trait when they  are either homozygous or heterozygous for it and ewes 
only when  homozygous.”   
Gonna guess maybe the  Sufflolk but that is a weak guess at best!? 
Would scurs be a  separate gene than full horns (like we see in Jacobs) or 
is this a modified  plus or minus kind of trait?   
Doggone & Chicken  UP! 
Tara Lee  Higgins 
Higgins Rat  Ranch Conservation Farm,  Alberta 
--  
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