Any feed store should carry beet pulp. Be sure to soak it well in warm water first before feeding as the pellets tend to expand quite a bit. I have heard of some horses choking on it. I have used beet pulp before to help an OTTB gain weight. It seemed to work, but I also added a handful of calf-manna to the feed along with a couple of tablespoons of corn oil. The horse also had free choice hay.