business of producing, processing, and distributing milk and milk products. Ninety percent of the world's milk is obtained from cows; the remainder comes from goats, buffaloes, sheep, reindeer, yaks, and other ruminants. In the United States, dairy products account for nearly 16% of the food consumed annually. California, Wisconsin, New York, Pennsylvania, and Minnesota are the top five dairy states. About 17% of the milk produced is made into butter, 35%–40% is sold as beverage milk, and the remainder is devoted to farm uses and the making of cheese, concentrated milks, ice cream, dried milk solids (e.g., lactose and casein), yogurt and sour cream, and other processed products. About 60% of total beverage milk sold is low-fat or skim milk, which surpassed whole milk in sales in 1987.
The development of modern dairying, which began around 1850, has been driven by the growth of urban markets and by scientific, technological, and economic factors: the invention of specialized machines, notably the cream separator (see separator, cream) and mechanized milking machines (and more recently automatic, or robotic, milking machines); research in chemistry, physics, and bacteriology; the discovery of pasteurization; the introduction of the test devised by American agricultural chemist S. M. Babcock for determining the fat content of milk; improved refrigeration and transportation; the discovery of new uses for the byproducts of milk processing; and increased milk productivity resulting from scientific feeding of cattle and the application of advanced biotechnology to breeding. Traditional small-scale dairy farms have increasingly been replaced by larger operations with herds of 1,000 cows or more.