My horse used to be on that senior feed.. we'd alter his feed by maybe 1/4 of a cup and he'd go NUTS! I switched him off of that as soon as I could to Safe Choice.. and he settled down. Then I put him on oats and whatnot because I didn't really like how little nutritional value was in that feed. He was great on oats.. but when I moved the new barn didn't want to feed oats so they started him on sweet feed and then we switched to Triple Crown Senior, and though he eats a lot of it, he is manageable on ground and under saddle and has enough energy to handle a good workout.
You just need to find what works best with your horse, which may be different from what someone else's horse works best with.
Good luck on the hunt!