I am sorry to hear that you have lost your horse to colic.
I notice that another poster has also posted information relating to another horse that had died through ragwort poisoning.

I believe that the symtoms of both colic and rw are pretty much the same in the early stages.

I am still astonished at the number of horses I see that are in fields with ragwort on the perimeters. Also need to mention the importance of keeping a horse moving whilst waiting for a vet with colic.

Sorry to have posted on your thread, just wanted to highlight these two dangers that many people (sadly) are so often unaware of.

Once again, I stress my sorrow to you having read of your tragic loss.