oats sugerbeet barley
Corn
Corn usually provides the most energy for horses. also Rolled oats.
a horse
More than 50% of the grain is used to feed cattle in the US. So most of the grain in the US is used to make meat.
Alfalfa hay gives the most energy and so does alfalfa based grains. Alfalfa is much like eating sugar, in how it can makes you hyper. Racehorses are fed this to have a better performance in races.
Grain is the most common feed you'd use to fatten up a beef bull for the freezer.
Rolled oats, corn, triple crown
The energy for the grain explosion comes from the dust's minimum explosive concentration (MEC), a measurement of particle size and energy nature. Most explosions occur at grain transfer points.
fats
almonds,
The horse will need more concentrated feed (oats/grain), more water, and more salt. Most people offer salt in block form freely; you can also feed electrolyte supplements or plain table salt in their grain.
Today, there are only a few thousand acres grown and much of it is sold as a feed grain. Most of the production is in the western states