[Jacob-list] skulls and SUED

[Jacobflock at aol.com]

I had to go to the garage to find two names; Larry Alderson and Betty  
Henson.  They did some studies on SUED that have been published in the ARK,  p. 
125-127 which covers SUED in several British breeds; Manx, Hebridean and  
Jacob.  Classification of the severity of SUED and incidence are  presented in 
tables with some statistical t tests.  
 
The gravity of the SUED defect in Jacobs in the US and Britian are graded  
differently but the defect seems to have a continuum.  The defect is  
relatively easy to detect by observing the eyelid but the orbit, the bony  
structure surrounding the eye is often claimed to be the source of the problem  
despite the intricasies of the complete eye structure; tissue, muscle and  
bone.  Even on a normal eye, the orbit may have a small notch (which can be  
felt by touch) through which the orbital nerves and blood vessels  pass. It 
seems that the notch is palpably larger with SUED at the graver  levels; but 
why?
 
The speculation on the cause remains confused: the bone or tissue  
arguments.  It is my sense that the speculation in the US is heavily on the  bone 
side. The linkage is the multiple horns cause the orbit to  split and 
therefore the eyelid is split.  The orbit roof is almost all  frontal bone; a small 
part of the roof is the sphenoid bone, part of the  sinus is also 
intersecting in the area of the orbit; vessels move through the  sinus and horns.  
Some present the cause as dependent on the location of  the lateral horns, 
others that it occurs with split fused horns.  The  linkage seems to explain the 
cause in terms of splits cause  splits. However, linkage may not be the 
cause.  The eyelid has little  connective tissue between the skin and muscle 
and to any underlying bone  structure.  Could it be that the problem we see, a 
 malformation of the upper tarsal muscle of the eyelid is not caused by but 
 another manifestation of a problem since the eyelid is not directly  
connected to the suprorbital fissure?
 
You might contact the polycerate breed associations in Scotland, England  
and Ireland and see if, as a group, they may be willing to collaborate on a  
project to identify the cause and move the ball down the field beyond a  
recessive defect for all polycerate breeds.  I would knock on a door at  
Glasgow University.
 
Fred Horak
St. Jude's Farm
1165 E. Lucas Rd.
Lucas, TX 75002

972-727-0900
 
 
 
In a message dated 9/19/2009 5:42:04 A.M. Central Daylight Time,  
westergladstone at btinternet.com writes:

Hi All
Skulls and SUED.  I know this is discussed every few  months - here in 
Britain it has come up again, this time on the Shetland  Breeders group.  You 
might not expect that, but every now and then four  horned individuals appear 
within the Shetland Breed and the incidence of SUED  in them is very high.
My question is:  has anyone over there in America,  where you are able to 
get your hands on your animals skulls, which we are not  here in Britain, 
seen any bony defect of the orbit in animals know to have had  split upper 
eyelids?
Of course everyone has their own ideas of the cause and  inheritance of 
four horns and SUED - here there are two main factions, one  saying that SUED 
is part of the split of the horns, extending down into the  bone of the 
orbit; the second opinion says that the defect is limited to the  soft tissues.  
I have seen skulls of four horned sheep known to have had  split eyelids, 
but with no bony defect and I have not seen one displaying a  defect, but my 
experience is very limited as we are not allowed to retrieve  skulls from the 
abattoir.
Your experiences would be very helpful - thank  you.
Juliet Johnston
Scotland  UK


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