The effects of dietary vitamin E and selenium deficiencies on plasma thyroid and thymic hormone concentrations in the chicken

Beginning at hatching. mate Cornell K strain single comb white leghorn chickens were fed a basal diet with or without vitamin E (100 IU/kg) and/or selenium (Se, 0.2 ppm). After 3 weeks of treatment, animals fed either the Se-deficient or basal diet had significantly reduced plasma Se-dependent glutathione peroxidase activities when compared to those fed a vitamin E and Se-supplemented diet. Similarly, animals fed the vitamin E-deficient or basal diet had significantly reduced plasma alpha-tocopherol levels, The effect of these treatments on plasma concentrations of thyroid hormones (T-3/T-2). growth hormone (GH), and thymic hormone (thymulin) was determined using radioimmunoassay and ELISA. A deficiency in Se. but not in vitamin E, resulted in an increase in plasma T-4 Concentrations while plasma T-3 concentrations were decreased. Plasma GH levels showed some fluctuation a, a result of the dietary treatments but there was no significant correlation between plasma GH levels and any of the other variables. A significant decrease in plasma thymulin levels was observed in Se-deficient birds compared to those receiving adequate Se in the diet. A vitamin E deficiency had no measurable effect on plasma thymulin levels. From these studies, we conclude that plasma thymulin concentrations directly correlate with plasma T-3 concentrations which are negatively affected by a Se deficiency. (C) 2004 Elsevier Ltd. All rights reserved.