COMPARATIVE NET ABSORPTION OF CHELATED AND INORGANIC TRACE MINERALS IN CHANNEL CATFISH ICTALURUS-PUNCTATUS DIETS

Coefficients of net absorption for copper, iron, manganese; selenium, and zinc mere determined for chelated sources (copper proteinate, iron proteinate, manganese proteinate, selenium proteinate, zinc proteinat e) and inorganic sources (copper sulfate pentahydrate, ferrous sulfate heptahydrate, manganese sulfate monohydrate, sodium selenite, zinc su lfate heptahydrate) of these elements with channel catfish Ictalurus p unctatus. Fish weighing approximately 60 g were placed into 40-L aquar ia (12 fish/aquarium) at a temperature of 28 +/- 2 C and fed either an egg white-based, purified diet or a soybean meal-based, practical die t with and without the test mineral sources for 6 wk then killed and f eces collected from the hindgut. Treatments were arranged in a 2 x 2 f actorial design. Absorption coefficients for the elements in the basal and mineral supplemented diets were calculated by the indirect indica tor (chromic oxide) method and corrected for residual amounts of eleme nt in the basal diets. Net absorption of the chelated minerals was sig nificantly higher (P < 0.05) than net absorption of the inorganic mine rals in both basal diets. Average percentage improvement in net absorp tion of chelated minerals over inorganic minerals was 39.3% in the pur ified diets and 81.1% in the practical diets. These results may indica te that appreciably lower amounts of chelated trace minerals than inor ganic trace minerals can be used as supplements in catfish feeds.