Common metabolic diseases of cattle: ketosis, milk fever, grass tetany, and downer cow complex.

Reid, in the 50th anniversary issue of the Journal of Dairy Science, stated that "in 1906, the average cow in the United States produced approximately 2,500 lb of milk; in 1956, she produced more than 5,000 lb." During the next 25 yr, the average annual milk production per cow has more than doubled, and some individual herds average more than 9,000 kg per cow per year. Selection of vastly improved strains of cattle in addition to increasing the potential for milk production also drastically narrows the nutritional and management spectrum over which these animals can maintain metaboli te homeostasis. Thus, proper nutri t ion and management of these high-producing cows become increasingly complex and critical. This review is not a comprehensive review of major metabolic diseases of cattle; rather, it is intended to be an interpretative summary. Emphasis will be placed upon progress during the last 25 yr, upon new techniques and approaches that have enhanced our understandings, and especially upon future areas in which research could be profitable or is needed strongly. We have reviewed major achievements as we see them in understanding pathogenesis of lactation ketosis, milk fever, grass tetany, and downer cow complex, and we have speculated upon future areas of research that seem worthy of additional investigation for these diseases. References will be limited to general