I know there aren't many digestible nutrients in oats (if any), but would they serve as a good "filler"? Kind of the horse equivalent of celery? Maybe ration out the oats with their regular feed to "dilute" it, probably not the right word to use, but perhaps adding some regular oats will make the horse think it's getting a lot more than it actually is?
Does anyone feed straight oats?
This is what I'm talking about