Copper poisoning in a dairy herd fed a mineral supplement.

Copper poisoning in a dairy herd resulted in the death of 9 of 63 (14%) adult Holstein cows. Clinical signs were acute anorexia, weakness, mental dullness, poor pupillary light reflexes, and scant nasal discharge. These were followed by recumbency, chocolate-colored blood, jaundice, and death. Four animals exhibited signs of hyperesthesia and/or rumen stasis prior to death. At necropsy there was generalized icterus of body tissues, with the liver appearing orange and the kidneys dark blue. Histologically, there was accumulation of hemosiderin in Kupffer cells, and severe to moderate hepatocellular necrosis in all cases. Ammonium molybdate added to the ration, combined with the cessation of mineral supplementation, arrested the outbreak.These cases illustrate significant mortality, due to copper poisoning, in adult cattle fed a low-dose mineral dietary supplement for over two years. Dietary copper intake of the herd (on a dry matter basis) was 37.5 mg/kg for lactating cows and 22.6 mg/kg for dry cows.