Biological availability of selenodicysteine in chicks.

The biological availability of selenium (Se) in selenodicysteine (SDC) for chicks was evaluated using plasma glutathione peroxidase (SeGSHpx) activity and tissue Se levels as criteria. In each of two trials day-old Single Comb White Leghorn chicks were fed a basal diet low in Se but supplemented with vitamin E during Days 1 to 14. On Day 15 three replicate groups of eight chicks were assigned to each dietary treatment. Dietary treatments consisted of feeding the basal diet alone or supplemented with approximately 50, 100, or 150 ppb Se as either sodium selenite or SDC from Days 15 to 27. Pooled samples of blood, liver, and breast muscle were obtained from four chicks per replicate group on Day 27. Activity of SeGSHpx and the concentration of Se in plasma, whole blood, muscle, and liver were highly correlated (P less than .0001) with supplemental dietary Se. In Trial 1 no differences were observed between the slopes for each compound upon determining linear regression equations for SeGSHpx, plasma Se, whole blood Se, muscle Se, or liver Se versus supplemental dietary Se. In Trial 2 there were no differences between the slopes for each compound in equations for SeGSHpx, plasma Se, or whole blood Se versus supplemental dietary Se. The ratio of slopes (SDC/sodium selenite) was .82 for both muscle Se and liver Se versus dietary Se. Thus, data indicate that Se in SDC is highly available for chicks.