Silage () is a type of fodder made from green foliage crops which have been preserved by fermentation to the point of acidification. It can be fed to cattle, sheep and other such ruminants (cud-chewing animals). The fermentation and storage process is called ensilage, ensiling or silaging. Silage is usually made from grass crops, including maize, sorghum or other cereals, using the entire green plant (not just the grain). Silage can be made from many field crops, and special terms may be used depending on type: oatlage for oats, haylage for alfalfa (haylage may also refer to high dry matter silage made from hay). Silage can be made using several methods, largely dependent on available technology, local tradition or prevailing climate. Production The crops most often used for ensilage are the ordinary grasses, clovers, alfalfa, vetches, oats, rye and maize. Many crops have ensilaging potential, including potatoes and various weeds, notably spurrey such as Spergula arvensis. Silage must be made from plant material with a suitable moisture content: about 50% to 60% depending on the means of storage, the degree of compression, and the amount of water that will be lost in storage, but not exceeding 75%. Weather during harvest need not be as fair and dry as when harvesting for drying. For corn, harvest begins when the whole-plant moisture is at a suitable level, ideally a few days before it is ripe. For pasture-type crops, the grass is mown and allowed to wilt for a day or so until the moisture content drops to a suitable level. Ideally the crop is mowed when in full flower, and deposited in the silo on the day of its cutting. After harvesting, crops are shredded to pieces about long. The material is spread in uniform layers over the floor of the silo, and closely packed. When the silo is filled or the stack built, a layer of straw or some other dry porous substance may be spread over the surface. In the silo, the pressure of the material, when chaffed, excludes air from all but the top layer; in the case of the stack, extra pressure is applied by weights to prevent excessive heating. Equipment Forage harvesters collect and chop the plant material, and deposit it in trucks or wagons. These forage harvesters can be either tractor-drawn or self-propelled. Harvesters blow the chaff into the wagon through a chute at the rear