My geldings are currently on a sweet feed and my mare is on a pelleted feed.
My mare has hypp (for those of you who don't know) and I feel i'm pretty educated on the disease, except for the feed part.
http://www.bringinglighttohypp.org That website suggests the use of Buckeye feeds. I went through them and I'm not sure which one would be best. So far, Vega is doing great on the pelleted feed, so I'm not up for changing it right now, but I do want to talk to my BO about it (she buys the feed and buckeye isn't sold where she buys it).
Vega is a 5 yo app mare. She is not currently in work. Work will start for her in the spring. She has not shown any symptoms. She is also NH.
If you need any more info, please let me know :)