Subchronic effects of sodium selenite and selenomethionine on several immune-functions in mallards

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The subchronic effects of selenomethionine (SeM) and sodium selenite (SeL) on several immunologic, hematologic, and serologic parameters in mallards were measured, using concentrations in drinking water of 0, 0.5, and 3.5 mg/L selenium (Se) as SeL and 2.2 mg/L (Se) as SeM. Cyclophosphamide (CP) was used as an immunosuppressive control at 20 mg/L. A battery ofin vivo andin vitro immunologic assays was performed on each bird throughout the 12 week study. The SeM-treated birds displayed a significantly impaired delayed-type hypersensitive (DTH) response to tuberculin (M. bovis), as measured by the number of positive reactions present 24 hours post PPD challenge (p ⩽ 0.05). The SeM-treated group also exhibited a significantly increased serum alanine aminotransferase (ALT) activity and an increased plasma glutathione peroxidase (GPX) activity (p ⩽ 0.05). Selenium concentration in the liver and breast muscle of SeM-treated birds was significantly elevated 4- and 14-fold, respectively, over controls (p < 0.05). Body weight and water consumption of treated birds did not differ from controls. Organ weights were not significantly affected by any Se treatment. Sodium selenite-treated birds displayed no detectable differences in immune-function or Se accumulation in tissues as compared to controls. Serum ALT activity was significantly increased in the 3.5 mg/L group, although to a lesser extent than in SeM-treated birds. Cyclophosphamide significantly depressed white blood cell number, testes weights, and also suppressed the DTH reaction. Concentrations of Se as SeL did not affect the immune system, whereas low concentrations of SeM (2.2 mg/L Se) appeared to suppress certain aspects of the mallard immune response.