Zinc Toxicity in Ruminants. III. Physiological Changes in Tissues and Alterations in Rumen Metabolism in Lambs

Abstract

Blood tissue and rumen fluid analyses on samples taken from lambs consuming 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 or 4.0 gm. of supplemental zinc per kg. of diet or receiving 0, 2.0, 4.0 or 6.0 gm. of zinc per head daily via a stomach tube revealed: High levels of zinc intake resulted in large increases in serum and organ zinc; the largest changes occurred in the liver, pancreas and kidney. High levels of zinc altered copper and iron metabolism as evidenced by decreased liver copper and increased liver iron. High levels of zinc in the diet of lambs decreased hemoglobin and packed cell volume values, while dosing with 4.0 or 6.0 gm. of zinc daily caused an increase in hemoglobin and packed cell volume. Some changes occurred in the metabolism of other minerals, as evidenced by changes in the levels occurring in the liver and bone; however, the alterations were not consistent among the experiments. Connective tissue replacement of acinar tissue was observed in the pancreas of lambs fed from 1.0 to 3.5 gm. of zinc per kg. of body weight. High levels of zinc altered rumen metabolism, probably through its toxic effect on rumen organisms.