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3 Agricultural Science (Animal) (continued) Crossbreeding is in common use by commercial swine, beef, and sheep producers. In addition, modern genetic engineering techniques are used for purposes of animal breeding. Livestock feeding Scientific livestock feeding involves the systematic applica- tion of the principles of animal nutrition to the feeding of farm animals. The science of animal nutrition has advanced rapidly in modern times, and the discoveries are being utilized by most of those concerned with the feeding of livestock. The nutritional needs and responses of the different farm animals vary accord- ing to the functions that they perform and to differences in the anatomy and physiology of their digestive systems. Likewise, feedstuffs vary in usefulness depending upon (1) the time and method of harvesting the crop, (2) the methods employed in drying, preserving, or processing, and (3) the forms in which they are offered to the animals. The various chemical compounds contained in animal feeds are divided into groups called nutrients. These include proteins, fats, carbohydrates, vitamins, and mineral matter. Proteins are made up of amino acids; 12 amino acids are essential for all nonruminant animals and must be supplied in their diets. Fats and carbohydrates provide mainly energy. Vitamins essential for health and growth include fat-soluble A, D, E, and K, and water-soluble thiamine, riboflavin, niacin, pyridoxine (B6), pantothenic acid (B5), and cobalamin (B12). Mineral salts that supply calcium, phosphorus, sodium, chlorine, and iron are often needed as supplements, and those containing iodine and cobalt may be required in certain deficient areas. Zinc also may be needed in some swine rations. In addition to their chemical composition or nutrient content, the nutritionist and livestock feeder should know the availability or digestibility of the differ- ent nutrients in feeds. Livestock disease and pest control The numerous diseases of farm livestock require expert diagno- sis and treatment by qualified veterinarians. The emphasis on intensive animal production has increased stresses on animals and generally increased the need for close surveillance of herds or flocks for disease outbreaks. Some diseases are common to several classes of livestock. For example, the following diseases may affect cattle, sheep, and goats: actinomycosis, anthrax, blackleg, brucellosis, leptospirosis, listeriosis, mastitis, pinkeye (conjunctivitis), and shipping fever (bovine respiratory disease). Other diseases generally affect only a particular species of livestock. The transmission of infectious diseases is a three-stage process involving the reservoir of the disease organisms, the mode of transmission, and the susceptible animal. A disease can be thwarted at each stage: at the reservoir by isolation and quar- antine, at the transmission stage by good hygiene, and in the susceptible animal by immunization and antibiotics. The most efficacious point for disease control varies with the particular disease etiology. Both external and internal parasites are common afflictions of livestock, but can be controlled by proper management of the animals. Sanitation is of utmost importance in the control of these pests; however, under most circumstances, sanitation must be supplemented with effective insecticides, ascaricides, and fungicides. Numerous other disease organisms pose a constant threat to livestock. Although many of these organisms can be treated therapeutically, it is much more advisable economically to establish good preventive medicine and health care programs under the guidance of a veterinarian. + ward ' s science 5100 West Henrietta Road • PO Box 92912 • Rochester, New York 14692-9012 • p: 800 962-2660 • wardsci.com This article was originally published by McGraw Hill's AccessScience. Click here to view and find more articles like this.