Hay ≠ silage. Hay is tedded and dried grass/straw. Hay is normally baled, but you can just throw it in a pile. Silage is grass that has been fermented to make it easier for cows to digest. Silage must be baled and wrapped, or stored in a silage silo so that it can ferment.
I grew up in farm country surrounded by pigs, horses, cows, and an absolute FUCKTON of tobacco, corn, and soybeans. Also a fair amount of weed if you knew which cornfields to go into.