Zinc Toxicity in Ruminants. IV. Physiological Changes in Tissues of Beef Cattle

Abstract

Blood and tissue samples were collected from calves on two toxicity experiments to determine the effect of high levels of zinc on blood components and tissue minerals. Results of the analyses suggest that: High levels of dietary zinc result in accumulation of high levels of zinc in the blood, liver, pancreas, kidney and bone, and lesser accumulations in the hair, spleen, lung and heart. High levels of zinc in the liver were accompanied by increased liver iron and decreased liver copper. Some effect was also noted on calcium, phosphorus and sodium content of the liver. Bone ash, calcium and phosphorus were not significantly affected by high zinc intake. Hemoglobin and packed cell volume decreased, when high zinc diets were consumed for an extended period of time. Steers had higher zinc levels and lower liver copper levels than heifers. When high levels of zinc were removed from the diet, the serum zinc decreased to almost normal levels within 6 weeks. Other liver mineral stores returned to normal at a much slower rate.