In cold areas of the world, harvested and preserved forage crops are essential in order to feed cattle and other livestock through the long winters. All of the common cereal grains are used to feed livestock as well as man. In Europe, many root crops such as beets, turnips and potatoes are also used to feed animals. Forage crops may be used directly, made into hay or into silage. Hay quality is determined by what species are involved, the amount of leaf material in comparison to stem material, the time the forage was harvested, and the amount of weathering and handling the material has undergone.
Ensilage is made by anaerobic fermentation of undried forage or the stalks of corn, sorghum, etc.
Ensilage is usually rich in water. During fermentation, the acid content rises and preserves the plant material. Most of the cultivated forage crops are from Europe or Asia. Most forage crops are perennials, but others are annuals. Table lists some of the major forage grasses.