A Pathologic and Toxicologic Evaluation of Veal Calves Fed Large Amounts of Zinc

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Abstract
Tissues were examined from 26 male Holstein veal calves given large amounts of dietary zinc. All calves had been fed 706 μg zinc/g of milk replacer for 28 days before the first death occurred. Calves died naturally (14, group A) or were euthanatized (12, group B) after 23 days of feeding a lower concentration of zinc (150 μg/g). Average amounts of zinc in liver (wet weight) were 345.72 μg/g (group A) and 344.84 μg/g (group B). Mean kidney zinc concentrations were 219.0 μg/g (group A) and 252.38 μg/g (group B). Tissue manganese, copper, and iron levels were normal. Changes at necropsy included pneumonia, fluid digesta, and petechiae and infarcts in liver, kidney, and heart (as a result of bacterial infections). Histological changes that were directly attributed to dietary zinc intake were: marked atrophy and necrosis of pancreatic acinar tissue (group A); multifocal fibrosis of pancreatic acini (group B); multifocal renal cortical fibrosis with necrosis in convoluted tubules and loops of Henle, and with intratubular mineralization (groups A and B). Hepatic midzonal mineralization and fibrosis of the adrenal zona glomerulosa were seen in group B calves.