ORGANIC SELENIUM SOURCES, SELENOMETHIONINE AND SELENOYEAST, HAVE HIGHER BIOAVAILABILITY THAN AN INORGANIC SELENIUM SOURCE, SODIUM SELENITE,IN DIETS FOR CHANNEL CATFISH (ICTALURUS-PUNCTATUS)

Channel catfish (Ictalurus punctatus) fingerlings (average initial wei ght, 1.70g) were fed casein-based purified diets supplemented with 0, 0.02, 0.06, 0.20 or 0.40 mg of selenium per kg from sodium selenite (N a2SeO3), selenomethionine (Se-M) or selenoyeast (Se-Y) for 9 weeks. Da ta for weight gain and glutathione peroxidase activity were subjected to regression analysis to determine dietary requirements and relative bioavailability for the various selenium sources. Broken-line analysis showed that minimum supplemental dietary selenium requirements as Na2 SeO3, Se-M and Se-Y for weight gain were 0.28, 0.09 and 0.11 mg kg(-1) , and for liver glutathione peroxidase activity were 0.17, 0.12 and 0. 12 mg kg(-1) diet. Relative bioavailability values of Se-M and Se-Y co mpared to Na2SeO3 were 336 and 269% for growth, and 147 and 149% for g lutathione peroxidase activity, respectively. Selenium from Se-M and S e-Y showed significantly higher rates of accumulation in liver and mus cle than selenium from Na2SeO3. This study indicates that selenium all owance in diets of channel catfish can be reduced when selenomethionin e or selenoyeast replaces inorganic selenium. (C) 1997 Elsevier Scienc e B.V.