Unstabilized rice bran is pretty cheap here, but I go through it pretty slowly and have read that it can actually go rancid before it actually hits the store shelves. Stabilized rice bran is $33 for 50 lbs, so much more expensive than beet pulp, which runs $12 for 40 lbs at my feed store.
Both rice bran and beet pulp are frequently used for weight gain, but have very different nutritional profiles. Neither are suitable as a sole ration (i.e. They aren't a good source of balanced minerals and vitamins) Rice bran is high in fat (>20%), phosphorous, and NSC (>20%). Beet pulp is high in digestible fiber and calcium, and unmolassed beet pulp is very low in NSC and thus much more suitable for IR horses. I like to mix a little rice bran into my beet pulp mash (I currently do 6 oz beet pulp pellets and 1 oz rice bran meal just for mixing in supplements); I think it gives it a better texture and makes it more palatable.
“The horse is a mirror to your soul. Sometimes you might not like what you see. Sometimes you will.” - Buck Brannaman
"Nothing forced can ever be beautiful." - Xenophon