Estimation of the relative bioavailability of inorganic selenium sources for poultry. 2. Tissue uptake of selenium from high dietary selenium concentrations.

An experiment was conducted with 192 day-old male Cobb chicks to study tissue uptake of Se as an estimate of the bioavailability of supplemental inorganic Se sources fed at high dietary concentrations. A basal corn-soybean meal diet (.18 mg Se/kg diet, dry matter basis) was supplemented with 0, 3, 6, or 9 mg Se/kg diet (as-fed basis) as either reagent grade Na2SeO3, CaSeO3, or Na2SeO3 plus fumed amorphous carrier or 6 mg Se/kg diet as either Na2SeO4 or Se metal, and fed for 1 wk. No toxic effects were noted as expressed by mortality; however, there was a reduction (P less than .01) in feed intake and daily gain when 9 mg Se/kg diet was fed, suggesting onset of toxicosis. Selenium concentration in liver, kidney, muscle, and plasma increased linearly (P less than .01) as dietary Se increased from all sources. Selenium metal produced lower (P less than .01) Se concentrations in kidney and muscle than other supplemental sources. Multiple regression slope ratios were used to estimate relative bioavailability values of 100, 103, 99, 112, and 83 for Na2SeO3, CaSeO3, Na2SeO3 + carrier, Na2SeO4, and Se metal, respectively. When these ratios were corrected for the analyzed dietary Se concentration, relative values were 100, 96, 94, 109, and 81 for the above sources, respectively.