I have found that my hard keepers and easy keepers do better on a 100% grain-free diet. I feed ADM's Metabolic Mineral pellets along with Alfalfa pellets and/or chopped Alfalfa hay (comes in a bag). You only need to feed 1-1.5 lbs of the mineral pellets a day, so it works great for my fatties. The hard keepers just get more of the alfalfa pellets to add more protein and calories to their diet. I also feed Uckele's Cocosoya oil to provide Omega 3 fatty acids as we don't have any real grazing to speak of.
Since swicthing to a grain-free diet my horses hold their weight better, have a better work ethic, their coats & feet are healthier, we have less issues with rain rot and thrush, my moody mare isn't as moody, and my spooky horses are much calmer. I will never feed any kind of grain or pellets that have any grain products again. No corn, no wheat, no "grain sweepings", or "grain by-products" will enter my feed room
The feed I use: StaySTRONG low starch mineral feed supplement
You can buy it online if you don't have an ADM retailer in your area. My ADM state sales rep delivers mine to me once a month
. The nearest ADM dealer to me is 2 hours away. They are a really great company!
I like the above feed because it doesn't have the high protein levels found in many ration balancers (often 30-35% protein). I know that 1lb of 30% protein isn't really that much protein, but they often add weird stuff to the feed to get the protein that high, like "egg product" or "whey protein" (milk!)... Sorry, my horse is an herbivore! Lol
A good article: http://www.admani.com/AllianceEquine...Challenged.htm