My old pony had to be tubed as well, it just wouldn't clear despite sedation, massage etc, we tried for 6 hrs before my vet ended up at midnight tubing him, the crap that came out was unbelievable, took over an hour to clear, he was blocked all the way to his stomach pretty much.
That was one mouthful of pony nuts, have never fed them to anything since, the old lad had eaten them all his life until that night.
