Effect of dietary phytate on growth and selenium status of chicks fed selenite or selenomethionine

1. An experiment was conducted to study the effect of dietary phytate on the selenium status of chicks fed on a semi-purified diet with or without supplements of sodium selenite or selenomethionine (200 micrograms Selenium/kg). 2. Assessment included measurement of growth and activity of glutathione peroxidase (GSHPx) (EC.1.11.1.9), an enzyme that limits damage by free radical species arising from oxygen metabolism by catalysing the reduction of hydrogen peroxide and lipid hydroperoxides. In addition, information was obtained on forms of selenium in blood, liver, kidney, heart and muscle, distinguishing between selenide-Se, reducible-Se and non-reducible-Se. 3. Phytate caused significant reductions in growth, food consumption and food conversion efficiency. Supplementary selenium was without effect on growth but significantly increased GSHPx activity in all tissues. Phytate also increased GSHPx activity in blood and heart, and in muscle in the absence of supplementary selenium, but decreased the activity in kidney. 4. Concentrations of all forms of tissue selenium were significantly increased by supplementary selenium. In general, there was greater deposition from selenomethionine than from selenite and most was in non-reducible form. 5. Phytate increased selenium in all tissues except muscle; it is not clear if this resulted from increased absorption or increased retention. It increased reducible-Se in blood, liver and heart and non-reducible-Se in blood and kidney. Tissue concentrations of selenide-Se were highly variable: presence or absence of phytate contributed to some significant interactions. 6. The results suggest that there is a positive relationship between phytate and selenium status in chicks, in contrast to its negative effect on growth.