When I first bought my mare about 6 years ago she was getting 1 scoop of a sweet feed mix that the stable provided twice a day. She was fine with this for years, and never had a problem.
Last August, I moved her to a different barn where she got the same amount, but it was a mix of sweet feed and cracked corn. She was fine with this, but I wanted something a bit more healthier for her.
For about the last 4 months, I switched her to only getting 1/4 of a scoop of the mix. (I originally wanted to use alfalfa pellets, but I couldn't find any near me.) And she gets 1 cup of Omega Horseshine and 2 scoops of ShoGlo a day. She's also been fine with this.
I just recently bought a 50lb bag of Nature's Essentials Enrich 32 Supplement. I'm hoping to stop using that sweet feed/cracked corn mix all together, and even the ShoGlo. I wouldn't go as far as calling my mare an easy keeper. She's just a pleasure horse; we do a lot of trail riding. I guess what I want is for someone to tell me that she'll be getting everything she needs with Enrich 32 and Omega HS, and of course all the grass hay she can eat. Nobody else at the barn I'm at really cares what their horses get. If the bag says "GRAIN" then that's what they get, so I feel like I'm talking to a wall when I try to ask them anything about this.