Have an older horse who shivers, it doesnt seem to affect him with his work that much, but have tried various methods to reduce the "shake". Cod liver oil fed with Cortaflex worked well, but had to be fed together, then changed to Aviform as it was cheaper than Cortaflex.
Have now discovered Eqifeast Winning Edge Gold, its amazing stuff, a complete overall suppliment which appears to have reduced the shivering considerably.
You may want to check out the Rural Heritage website. Dr Beth Valentine and Dr Stephanie Valberg (both in America) have done much research into this. It is related to EPSM and can be considerably improved with diet adaption.
I have a 6year old who shivers. Currently we event at intro level. His shivers wasn't noticeable when ridden - he had an occasional 'odd' stride on his left hind when in free walk - until about a month ago. Now as his head goes down so his rear hind comes up - an exaggerated step but just on one leg.
There seems to be different thoughts on what causes it but no definitive answer. There was research going on in america to determine if the condition was hereditary - it was due for publication back end of last year but I haven't seen it as yet.. it seems it is becoming more evident in dutch warmblood (which mine is)
Thanx for your replies! My boy has shivers but ive owned him for a year and a half and its not got any worse, it doesnt seem to bother him really. Ive got a very good understanding farrier who takes his time with him and understands his problem. He's a fantastic jumper and has awesome paces, so it really isnt a problem! But he's not a very good loader, and some people have said this could be to do with his shivers. But unless you talk horse it would be hard to ever tell i guess! x