Environmental molybdenum levels in industrial molybdenosis of grazing cattle

Abstract An important molybdenum field study was carried out over four years in the environment of a steelworks to establish a comprehensive dose-effect relation. A survey of molybdenum concentrations in samples such as suspended particles, fallout deposits, soil and pasture was carried out using three methods of determination (atomic absorption, spectrophotometry, pulse polarography) the results of which are compared. The study shows that low levels of molybdenum in suspended particles (5–40 ng m −3 ) in fallout deposits ( −2 month −1 ) correspond to a pasture molybdenum content from 2 to 20 ppm (dry matter). Associated with a slight copper deficiency of natural origin, such levels of molybdenum lead to a molybdenum-induced copper deficiency resulting in the appearance of symptoms such as diarrhoea, loss of coat colour and unthriftiness when the Cu/Mo ratio in pastures is below 3. Affected cattle show an important improvement after injections of copper glycine.