Old OTTB not eating: Most palatable horse feed?

I didn't read all the replies, but have you tried triple crown senior? I haven't met a horse yet that didn't absolutely love it(even the picky ones I know).

I agree with not adding more rice bran if you are already feeding 1.5lbs I think you're not supposed to feed more than 2lbs a day. I don't know if you have tried this but what I did with my picky eater for awhile when she was on rice bran was mix the rice bran (warm) with her pelleted feed and she loved it!! Good luck with your horse, she is definitely lucky to have a great owner her takes as good care of her as you do!! :)