There were no sheep in with the bull,nor were there any within sevral miles.
As suggested above,the only possible thing it could have been (besides a viris) could be a foriegn object in the stomch.
It has been on my mind for a while.
My grandfather had a very healthy bull. He had access to a large pasture and twenty five head of cows. Then all of a sudden he showed signs of pnumonia. He wouldn't eat or drink. The vet gave him a shot and he still kept getting skinnier. He died one day...