I took in an OTTB, 3 year old, who was already on a lower grain ration when he came, due to lameness issues. He ate at my place: free choice grass hay and a low Carb feed for racehorses at risk of tying up. Saltlick, turnout in drylot. Second day( feed mixed with his old stuff), he colicked, when vet arrived he was already okay again.
His manure, in fact, the whole horse, smelled...sour, sharp. Hard to explain. When I opened the barn in the morning I couldn't do the Backdoor fast enough. That bad!
He was normal, with above feeding, after 6 months. I wasn't aware of hind gut acidosis then.
My new horse came, slightly on the thin side. He ate at his old place hay only, half forage hay(wheat-oat-barley) and half grassy alfalfa. That's common here. He always pulled his belly up a little. For about a week now I've been giving him more alfalfa and grasshay, just a handful of forage hay. He also gets soaked alfalfa pellets, rationbalancer and flax. Now belly is relaxed.
So I guess I had two cases myself:-/