Selenium accumulation and loss in mallard eggs

Five female mallards (Anas platyrhynchos) that had just started egg laying were first fed a diet containing 15 ppm selenium in the form of selenomethionine for 20 d and then an untreated diet for 20 d. Selenium levels in eggs peaked (to about 13-20 ppm) in about two weeks on the treated diet and leveled off at a low level (< 5 ppm) after about 10 d back on the untreated diet. Selenium levels in egg whites responded faster than levels in yolks to the females' consumption of treated and untreated diets.