Oats
Probably the most common grain fed to horses, oats can be fed whole, crushed, rolled, bruised or processed into grain. On the whole, processed oat grain is easier for horses to digest – although it looses some of its nutritional value if kept more than a few weeks.
Corn
Corn provides a high energy content and is known as a hot feed. Corn grain is usually fed in small amounts as a supplement to feed & is more often fed to cattle than horses. Although equines can eat corn whole, it is more beneficial to them if it is cracked.
Barley
Provides more energy content than oats, but less than corn & is often used to improve an animals condition, put on weight or improve coat. Barley grain is of greatest nutritional value when it is boiled before being fed.
Milo
Milo is also called sorghum and is a small, hard grain that cannot be properly digested by horses unless it is ground, rolled or boiled.
Soybean
Soybean meal is a good source of protein & much easier to digest when the husks are removed.
Wheat
Feeding wheat grain to horses is not recommended and is known to cause founder. If fed, it should be crushed or boiled and only in very small quantities.