[Jacob-list] skulls and SUED

[BlackSheep]

Fred, thank you so much for your reply and the efforts you have made for me. 

To tackle the last bit first: 
<<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.>>
Gordon and I are part of a group which is doing just that !  Gordon is the Vice Chair of the Hebridean Sheep Society, which has begun to look at the inheritance of 4 hornedness and SUED, with an ultimate goal of being able to supply breeding advice to polycerate breeders.  The Manx Group and some Jacob breeders are also on board, as are Lawrence Alderson and Libby Henson - Britain is a small place !!
So, it is because of my involvement in this research that I have approached the Jacob list to see what evidence you might have in North America.  As I mentioned in my first email, here in Britain we have very strict controls on the disposal of spinal and brain tissue - it was even for a while impossible for us to get back our sheeps horns from the abattoir, although there was such a huge protest at that that we can get them now. But it does mean that we cannot get skulls.  
We have approached various universities but funding is an insurmountable problem there.  We had hoped that a PhD student could make this their project - two difficulties there, again funding, but also that a PhD doesn't carry the research any further, as was the case with Libby Henson's work - she came up with some possible causes and associations at the end of her paper, and of course stated that further research is needed to continue to address the issues, but there it has stood for years now.  Libby works for the Rare Breeds Survival Trust in Britain, but is not in a position to do further research in spite of her continuing interest. We do have a final year vet undergrad in the group and perhaps she will stay on for a PhD..........
The Hebridean Sheep Society is very small and poor, and multi horns currently make up only about 6% of the Hebridean national flock (it was 60% in the 1970s), so we would be totally unable to begin to fund research ourselves.  As well as physical findings, we would like to see the questions about polycerates and SUED studied at a genetic level.  I understand from Gary Anderson's email to me that Janine Fenton was hoping to interest a university in Colorado in these questions, so I would love to be able to correspond with her.  Although if she had been successful it is likely that we would all have heard about it.

You mention that in the US you grade the eye defect differently.  Here we have: type 1 - normal eye, type 2 - break in the pigment line (ie a brief change of colour from dark to light and back) and fine for breeding males and females (I have reservations about even mentioning this almost invisible difference), type 3 - a small break in the eyelid, shaped like a small notch, and 4 - type 4 which is a severe split expending into the body of the eyelid, and can sometimes be so severe that it shows as a scar on the cornea.  It is recommended that males with types 3 and 4 should not be used for breeding and that females with type 4 should be carefully assessed and only used in the breeders flock if they have other traits which are important, but should not be sold on (this is for Hebrideans - I think the JSS says neither sex should be used for breeding with a type 3 or 4 defect - the difference is that there are plenty of 4 horned Jacobs to choose from, but 4 horned Hebrideans are very rare so we cannot be too strictly selective at this early stage).

Fred, your comments about the bony structure of the sheeps skull are of great interest to me.  I am currently trying to find a skull to take a closer look at, so I can see what is normal - quite important before trying to decide what is abnormal !  As soon as we get our tup lambs in again, Gordon and I will try palpating the orbits of the normal and one abnormal ones we have.  I feel that until we have a number of such skulls to compare, normal with those from animals with SUED, we can only speculate.

Thank you again for your reply.

Juliet in Scotland
ps as Gordon wrote privately to you, Marshall Watson is still on the go.  He no longer keeps Jacobs, Soay or Hebrideans, just Shetlands, but is in contact with the group we have started, sharing his opinions with us, and is a friend - he lives only 11 miles away and we bought our first ever Hebridean tup from him.  Small country again !

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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
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