Store concentrates to maintain quality
Concentrates should be stored in grain bins, barrels, or feed boxes with tight lids to keep them dry and prevent spoilage. These storage devices also prevent rodents and insects from damaging the grain.
All feed rooms should contain a small scale to weigh out the appropriate amount of feed. Remember, horses are fed as a percentage of their body weight. A simple bathroom scale will work.
To prevent grain from becoming moldy and spoiling, do not store more than a one-month supply, and rotate leftover grain so it is fed first when new grain is purchased.
Hay should be stored in a dry, clean environment. Moisture causes mold to grow on the hay, and moldy hay should not be fed to horses. Also, hay should not be exposed to the elements, which could decrease the hay's nutrient quality and cause browning or yellowing.
From eXtension HorseQuest.