[Jacob-list] Occypital condylar dysplasia

[Pbs123 at aol.com]

In a message dated 4/19/02 6:28:46 AM Eastern Daylight Time, 
iseespots at prodigy.net writes:


> Does anybody know if this disease is congenital or genetically transmitted? 

       Definitely inherited, but the source is debatable, in my opinion. You 
always want to think of inbreeding, but with jacobs it could be part of the 
spectrum of problems associated with polyceratism, such as SUED, and the 
notches on the boney orbit. When OCD is present, usually the entire rear of 
the skull is somewhat malformed as well.
       The very first time I examined a jacob head post mortem I noticed that 
the hole in the rear of the skull through which the spinal cord exits (the 
foramen magnum), was disproportionately small and misshapen. With time I've 
noticed that almost every mature male jacob has a relatively small foramen 
magnum, some astonishingly so, to the point that it must have caused motor 
problems (ataxia) in life. Other breeds of sheep, on the whole, have larger 
foramen magnums. And white-tailed deer,  ruminants of similar size, have 
absolutely huge openings in comparison.
       Over time I noticed that severely malformed "atlanto-occipital" joints 
were surprisingly  pervasive in jacob rams, but I also discovered that 
manifestations in living rams where almost nil. Almost all breeders whose 
sheep showed moderate-severe OCD had no recollection of any problems when 
asked. Some of the rams had joints so malformed that the head must have 
listed to one side (torticollis) but if so it went unnoticed.
It was later that Fred Horak sent me a copy of an article that was apparently 
written by vets that had observed and named OCD when doing a necropsy on 
sheep that exhibited symptoms like those detailed in the post to the list. 
The point is, from what I've seen the dysplasia in this instance would have 
to be dramatically severe and thus easily observed in a necropsy.

Peter S
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