Comparative Effects of Inorganic and Organic Dietary Sources of Selenium on Selenium Levels and Selenium-Dependent Glutathione Peroxidase Activity in Blood of Young Turkeys

Abstract

The effect of various dietary sources of Se on Se-dependent glutathione peroxidase (SeGSH-Px) activity in plasma and whole blood was studied in turkeys. Dayold poults were fed low Se diets (supplemented with vitamin E) for 15 to 24 days before being fed experimental diets for 7 to 10 days. Menhaden fish meal (0.1 ppm Se) increased plasma SeGSH-Px activity by 45% of the response to 0.1 ppm Se as Na2SeO3. Poults supplemented with 0, 0.1, 0.2, or 0.4 ppm Se as Na2SeO3, had similar increases in plasma and whole blood Se levels; however, SeGSH-Px activity of plasma (r = 0.96) was better correlated with dietary Se than that of whole blood (r = 0.64). The supplement of 0.4 ppm Se increased the activity of SeGSH-Px almost 20 times in plasma but only 1.6 times in whole blood. The effectiveness of several compounds providing 0.2 ppm Se for increasing plasma SeGSH-Px activity was: Na2SeO4 > Se-dl-cystine > Se-dl-methionine and Se-dl-ethionine. The effect of Na2SeO3 was not significantly different from that of Se-dl-cystine, Se-dl-methionine or Se-dl-ethionine. The ratio of SeGSH-Px activity:Se concentration, indicating the amount of Se associated with enzyme activity, was highest in plasma of poults fed Na2SeO4 andSe-dl-cystine. The data demonstrate differences in the availability of various Se sources for SeGSH-Px activity in poults.selenium glutathione peroxidase turkeys fish meal