FEED

also called Animal Feed, foodstuff grown or developed for livestock and poultry, selected and prepared to provide highly nutritional diets that will both maintain the health of the animals and increase the quality of such end products as meat, milk, or eggs. The feeds produced today are the result of research, experimentation, and chemical analysis and are the subject of continuing study by agricultural scientists. Livestock and poultry feeds are derived from crops grown specifically for that purpose, such as hay or pasture grass, by-products of foods produced for human consumption, or those rendered from surplus crops. Most diets, however, involve a combination of feeds from these sources. Animal feeds are divided into two general categories: concentrates and roughages. The concentrates are rated high in terms of the digestibility of their nutrients but low in fibre content, while the roughages are high in fibre and comparatively low in digestive nutrients. The concentrates include wheat, corn (maize), oats, rye, barley, and the sorghums. Such cerealsprocessed whole or ground and generally mixed with supplements, vitamins, and mineralsare easily digestible and rich in starch. Other concentrates include the high-protein meals that are made from such vegetable seeds as soybeans, field peas, peanuts (groundnuts), sunflower seeds, and cottonseed. Still other forms of concentrate foods are the by-products that have been developed from foods processed for human usage, including supplements made from carbohydrate-rich sugar beets and sugarcane and a molasses from citrus fruits; the residues from cereal grains, such as wheat or rice bran, wheat-germ meal, and hominy; animal by-products; and dried dairy foods made from skim milk, buttermilk, and whey. The most commonly cultivated roughages, as well as the most widely used livestock feed, are pasture grasses and plants. Pasture is highly nutritious, rich in protein and vitamins, and much cheaper to grow for grazing than feed products that must be harvested. Second in importance are the various kinds of hay, which are produced by drying grasses and legumes. The hay is dried in order to preserve nutrients that can be lost by exposure to rain and prolonged sunshine. Legume hay, such as alfalfa or clover, is the richest in protein. Other forms of roughage include silage, which comprises such green forage plants as corn, sorghum, and grass that are preserved and stored in silos; root crops, including rutabagas and mangels; straws made from cereal grains; and corncobs and the hulls from rice and cottonseed. Livestock and poultry require approximately the same nutrients as human beings, the most basic of which are protein, carbohydrates, fat, minerals, and vitamins. Proteins, made up of various amino acids, aid in the maintenance and repair of muscles, tissue, and internal organs. Protein is most important in the diets of pigs, poultry, and the young of livestock. It is of minimal importance to full-grown cattle, sheep, and goats. Those feeds with the highest protein composition include such concentrates as fish meal; meat and bone meal; poultry waste; meals made from soybeans, peanuts, and sesame seeds; and brewer's yeast. None of the roughage feeds have a high protein rating. Carbohydrates and fats are the nutrients that are converted by animals to provide heat to maintain body temperature and energy for growth, strength, and the maintenance of vital bodily functions. Simple carbohydrates, such as starches and sugar, are highly nutritious and easily digestible; complex carbohydrates, like those from the fibre of plants, are much less digestible and are important only to cattle, sheep, goats, and other ruminants. Fats are strong energy producers and are highly digestible. Cottonseed, soybean seeds, rice bran, and poultry waste are especially high in fats. Most roughage is high in fibre, especially the various hays, corn fodder and cobs, straws, sorghums, and the hulls of cottonseed, rice, and soybeans. Mineral nutrients required by animals include sodium chloride (salt), calcium, phosphorus, sulfur, potassium, magnesium, manganese, iron, copper, cobalt, iodine, zinc, molybdenum, and selenium. The proper balance of minerals is achieved in animal diets through supplements and additives, although salt is often provided separately on a regular basis. Among the vitamins needed by animals, the one most often lacking in basic animal feeds is vitamin A. It is especially important for growth, reproductive quality, and resistance to various diseases and infections. Green-growing crops are rich in carotene, a substance that animals easily convert to vitamin A. Vitamin D is also important in order to enable animals to assimilate and use calcium and phosphorus. Field-cured hay, fish oil, and other feed oils are good sources of vitamin D. also called animal feed, foodstuff grown or developed for livestock and poultry, selected and prepared to provide highly nutritional diets that both maintain the health of the animals and increase the quality of such end products as meat, milk, or eggs. Many of the feeds produced today are the result of research, experimentation, and chemical analysis and are the subject of continuing study by agricultural scientists. Animals in general require the same nutrients as humans. Some feeds, such as pasture grasses, hay and silage crops, and certain cereal grains, are grown specifically for animals. Other feeds, such as sugar-beet pulp, brewers' grains, and pineapple bran, are by-products remaining after a food crop has been processed for human use. Surplus food crops, such as wheat, other cereals, fruits, vegetables, and roots, may also be fed to animals. History does not record when dried roughage or other stored feeds were first given to animals. Most early records refer to nomadic peoples who, with their herds and flocks, followed the natural feed supplies. When animals were domesticated and used for work in crop production, some of the residues were doubtless fed to them. Preservation of green forages such as beet leaves and corn (maize) plants by packing them in pits in the earth has long been practiced in northern Europe. The idea of making silage as a means of preserving and utilizing more of the corn plant was gradually developed in Europe and taken from France to the United States in the 1870s. When the mature, dried corn plant was fed to cattle in the winter, much of the coarse stem was wasted, but when it was chopped and ensiled (made into silage), everything was eaten. The first effort to evaluate feeds for animals on a comparative basis was apparently made by Albrecht Thaer (17521828), in Germany, who developed hay values as measures of nutritive value of feeds. Tables of the value of feeds and of the requirements of animals in Germany followed and were later used in other countries. Present-day knowledge represents an expansion and improvement of these early efforts. Additional reading Textbooks and reference works that are useful sources of information on animal nutrition include Oskar Kellner, Kraft Drepper, and Klaus Rohr, Grundzge der Ftterrungslehre, 16th completely rev. ed. (1984); Leonard A. Maynard et al., Animal Nutrition, 7th ed. (1979); Arthur E. Cullison and Robert S. Lowrey, Feeds and Feeding, 4th ed. (1987); Peter R. Cheeke, Applied Animal Nutrition (1991); and D.C. Church, Livestock Feeds and Feeding, 3rd ed. (1991). John K. Loosli The Editors of the Encyclopdia Britannica