I'm one of them
Oat hay is cut when the oat kernels are in the dough stage. So the "oats"are still in vs in oat straw the oats are out and the straw is used as bedding or to "thin down" high calorie hay like alfalfa.
I was thinking of giving my 2 geldings that are on the chunky side a round oat straw bale, (that still has a little green in it and a little oats) to munch on to keep them busy and then control feed the hay. Winter is coming so I want them to have something always and don't want them obese or chewing fences out of boredom. Would this work?
An old term for oat hay is green feed. It is cut before it starts heading out. We fed it one winter and horses did well. Oat straw has ripened and been harvest of it's grain when it has turned yellow. Often one will find a few oats remaining within the bale. When there's a shortage of hay, a flake of oat straw can be fed as it provides the roughage the gut needs.
I new what green feed was, just didn't know if it was the same as oat hay. We don't have any green feed around and oat straw is scarce, but I found someone with round oat straw finally. I usually use it as bedding, but thought it would keep the boys busy if I put it in the feeder. I had them on the slow feed net with hay , but they are getting to fat
I usually do give a little of the oat hay on the ground too, they pick the oats out, the rest stays on the ground. I use that as bedding in their shed. My oat hay is cut pretty late, its somewhere between actual hay and straw.