Julio L. Pimentel

Iron metabolism in chicks fed various levels of zinc and copper

Abstract Four studies were conducted to determine the effect of high levels of zinc and copper on iron use of the chick. Chicks from the cross of New Hampshire x Single Comb White Leghorn were fed semi-purified diets with adequate (0.58–0.76 μmol Zn/g diet) and high (26.0–31.4 μmol Zn/g diet) levels of zinc and adequate (0.13–0.17 μmol Cu/g diet) and high (3.18–3.50 μmol Cu/g diet) levels of copper for 21 days. Fe-59 was fed in studies A–C and injected intraperitoneally in study D. Chicks fed high levels of zinc consistently showed decreased packed cell volumes and depressed concentrations of iron in livers and tibius. The anemia was not attributable to reduced feed and iron intakes. Chicks fed high rather than adequate amounts of zinc excreted 78% rather than 54% of an oral dose of Fe-59. The appearance of Fe-59 in plasma 1 hour after feeding the isotope decreased in chicks fed high rather than adequate levels of zinc. Ingestion of additional copper did not reverse the effects of ingesting high amounts of zinc on iron absorption. Ingestion of the high levels of zinc had minor effects on endogenous iron excretion. The ingestion of additional copper partially counteracted this effect.

Anemia induced by ingestion of excess zinc in chicks: importance of red blood cell turnover?

Abstract Three studies were conducted to determine whether ingestion of excess zinc induces anemia, at least partially, by increasing red blood cell fragility directly or through changes in copper-zinc—dependent superoxide dismutase (Cu-Zn-SOD). Chicks from the cross New Hampshire × Single Comb White Leghorn were fed adequate (0.72–0.76 μmol Zn/g diet) or high (22.60–25.17 μmol Zn/g diet) levels of zinc and adequate (0.11–0.14 μmol Cu/g diet) or high (3.13–3.45 μmol Cu/g diet) levels of copper. To assess whether excess zinc could induce a hemolytic anemia, we monitored red blood cell (RBC) Cu-Zn-SOD, RBC fragility in vitro, and erythrocyte t 1 2 in vivo. Cu-Zn-SOD activity was depressed among chicks fed excess zinc and the ingestion of extra copper restored Cu-Zn-SOD activities to the levels of the control chicks. However, lysis of erythrocytes in diluted saline (0.35% NaCl) was lower when chicks were fed high levels of zinc and the ingestion of extra copper further decreased lysis. With these counteracting influences, the lifespan of erythrocytes was not affected by any of the treatments in one study and was greater in chicks fed both high zinc and copper in another study. These data indicate that the anemia induced by excess zinc is not a hemolytic anemia.