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Objective To describe a case of acute, fatal molybdenum poisoning in feedlot cattle. Description of the herd In total, 831 Hereford, Hereford x Angus, and Hereford x Simmental steers, aged 8 to 10 months, with an average body weight of 310 kg were fed a diet, to which sodium molybdate at a rate of 1.9 % of the total ration had been accidently added. Investigation The steers lost appetite within 3 days and deaths commenced within 6 days of the diet being first offered. The error was rectified when deaths started to occur, but steers continued to die for up to 7 months afterwards. Of the 831 steers on the feedlot, 90 died and a further 5 remained in poor condition. The cause of death was periacinar to massive hepatic necrosis and acute renal tubular necrosis. Blood and tissue samples were taken from surviving steers for 76 days, by which time plasma molybdenum concentrations had returned to normal concentrations. Conclusion Sodium molybdate when fed at a rate of 1.9 % of the diet results in acute renal tubular necrosis and periacinar to massive hepatic necrosis.