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Physiological Responses of Calves to Cadmium and Lead

U.S. Department of Agriculture, Beltsville, 20705

Abstract

Twelve Holstein steer calves were dosed with 9 mg lead (Pb), 18 mg Pb, 15 mg cadmium (Cd), 10 mg Cd + 14 mg Pb, or 15 mg Cd + 18 mg Pb/kg body weight; and one pair was the control. Doses were PbCO₃ or CdCl₂ and were given three times weekly for a 12-week period. Only data for the first 6 weeks of treatment were analyzed statistically. Determinations were made weekly for hemoglobin (Hb), activity of -aminolevulinic acid dehydrase (ALAD), erythrocyte counts, leucocyte and differential counts, and blood concentration of Cd and Pb. Calves were observed for abnormal clincial signs. Liver and kidney tissue samples were obtained for light microscopy and electron microscopy examination. Oral dosing of calves with both Cd and Pb for the 6-week period reduced feed intake (P<.01) and body weights (P<.01) at treatment dose levels up to 18 mg Pb. Both Cd and Pb dosing reduced erythrocyte ALAD activity at all doses (P<.01). Treatment with Pb gave the greatest inhibition; Cd was intermediate in effect. Erythrocyte Hb concentration was reduced (P<.01). The Pb-treated calves showed the lowest Hb levels. During the first 6 weeks of treatment, erythrocyte count increased (P<.01). Leukocyte count was not changed, but the percentage of lymphocytes increased (P<.01) and the percentage of neutrophils (P<.05) and monocytes (P<.01) decreased. Treatment increased blood Cd and Pb (P<01). Calves receiving up to 18 mg Pb survived 84 days, but calves receiving Cd or Cd + Pb had shorter survival times. Abnormal signs included incoordination, circling, blindness, gastritis, ecchymotic and petechial hemorrhages of the gastrointestinal tract, and edematous kidneys. Basophilic stippling was evident after 5 weeks of Pb treatment. Erythrocytes were crenated and irregular in shape, with the appearance of many immature nucleated erythrocytes. Kidney cells of proximal convoluted tubules contained intranuclear inclusions due to Pb treatment. Liver cells contained frequent dark staining lysosomes.

¹ Nutrition Institute, Agricultural Research Service, U.S.D.A.

² Animal Physiology and Genetics Institute, Agricultural Research Service, U.S.D.A.

³ Biometrical Staff, Agricultural Research Service, U.S.D.A.