Effects of inorganic and chelated trace mineral (Cu, Zn, Mn and Fe) premixes in marine rockfish, Sebastes schlegeli (Hilgendorf), fed diets containing phytic acid

Abstract

The present experiment was conducted to evaluate the effects of trace mineral (Cu, Zn, Mn and Fe) premixes from inorganic and chelated (chelated to 2-hydroxy-4-methylthiobutanoic acid or hydroxy analog of methionine; Mintrex™, Novus International Inc., St. Charles, MO, USA) sources, in rockfish, (Sebastes schlegeli). fed diets containing mineral inhibitor phytic acid. Seven isonitrogenous (46% crude protein/CP) and isocaloric (16.63 KJ available energy per g diet) semi-purified diets comprising of a Basal control and diets supplemented either with the inorganic (I) or chelated premix (M) at three different levels of 0.75 (I0.75/M0.75), 1.5 (I1.5/M1.5) and 3 (I3/M3) g kg−1 diets were formulated. Twenty-four fish averaging individual wet body weight of 9 ± 0.2 g (Mean ± SD) were fed one of the experimental diets in quadratic group for 16 weeks. Average weight gain (WG) of fish fed M3 was significantly higher than that of fish fed Basal control and I1.5 diets (P < 0.05). Whereas, data for the liver and whole body trace mineral contents showed a higher Cu and Zn saturation among fish fed M3 and M1.5 diets (P < 0.05). Furthermore, hepatic Cu-Zn super oxide dismutase (Cu-Zn SOD) activity was recorded to be highest for fish fed M3 diet. Whereas, hepatic thiobarbituric acid-reactive substance (TBARS) value was lowest in fish fed M3 diet (P < 0.05). Challenge test with E. tarda showed an improved disease resistance among the fish fed different levels of trace mineral premixes. Therefore, these results demonstrated a higher efficiency of chelated compared to inorganic source of trace mineral premixes in marine rockfish.