My horses don't get grain, but they do get a pelleted vit/min supplement, a small amount of pelleted rice bran, and Omega-3 Horseshine.
I prefer the Omega-3 Horseshine to plain flax because it has the appropriate ratio of Omega-3 to Omega-6. An overload of either (6 more than 3) is not good.
Omega-3 Horseshine has really gone up in price the last couple years but, you only need to feed a 1/2 cup (household measuring cup) daily. I divide that into two feedings.
Everyone got taken off dry grain and switched to rice bran when the horse in my avatar became Insulin Resistant two years ago. They all only get a token amount - 1-1/2 household measuring cups divided into two feedings.
Even the I-R horse is maintaining his weight on that little amount. The other three don't even need that, but I call it "filler" to mix their supplements in and it makes me feel like I fed them something
Not that it makes any difference, but three of my horses are also Tennessee Walkers, and the fourth is an Arab I rescued 16+ years ago looking like a starving horse poster child. The Arab is now 23, the TWH that is I-R is coming 22 and both do terrific without grain.
Please don't take offense but I learned 11 years ago that sweet feed is the worst possible thing to feed a horse. It is cheap to feed but it's like feeding a gallon of Hi-C and two dozen Hershey bars to a 10 yr old boy. It takes a lot more sweet feed to maintain a horse than even a dry grain-based feed.
The person that got me off sweet feed owned the feed store I bought from and also owned race horses. His very kind words were to "--do my horses a big favor and quit feeding them that stuff-".
He carried sweet feed and sold it, but for some reason he felt safe telling me to get my horses off it and spend more money on a good feed that I wouldn't have to use as much. I actually ended up saving money by feeding less and had healthier and less hyped-up/nervous horses for it