Now you mention it, it has made me think back to last winter.
I fed Baron oats all winter and he had filled legs every morning, the went down after about 2mins of walking though.
I keep him in sometimes in the summer before a comp and his legs do not fill, and he is no longer on oats. Also he was on box rest for a week during the summer and his legs did not fill.
I have never found that personally, a few horses at my yard are fed oats and none of them have had filled legs allthough its all about the indivitual horse I suppose
Sorry to disagree, but oats (or any high starch/protein feed) can cause filled legs if the horse is not receiving sufficient exercise to use the energy given by the feed. Either ride him more, or feed him less.