Evaluation of Elevated Dietary Aluminum and Iron on Red Drum, Sciaenops ocellatus

This study was conducted to determine if relatively high dietary levels of aluminum and iron might affect growth, mortality, and mineral content of red drum, Sciaenops ocellatus, because algae coproduct may have rather high aluminum and iron levels due to the algae harvesting and extracting processes. Experimental diets were prepared by supplementing different levels of aluminum (1000, 2000, 4000, 8000, and 3000 mg/kg diet) from aluminum sulfate, or iron (1000, 2000, 4000, and 8000 mg/kg diet) from ferric sulfate, or a combination of aluminum and iron (4000mg Al/kg and 4000mg Fe/kg) to a basal diet which was formulated from practical ingredients and analyzed to contain an average of 526mg Fe/kg and 1940mg Al/kg diet. The feeding trial was conducted in a recirculating system consisting of 38-L aquaria maintained at 7 ppt salinity with synthetic seawater and sodium chloride. Each diet was fed to triplicate groups of 12 juvenile red drum initially averaging 4.5 g/fish for 7 wk. At the end of the feeding period, there were no significant differences in average weight gain, feed efficiency, or hepatosomatic index of fish fed the various diets. Significant differences were found in liver iron concentration (P=0.045) but not iron concentration of whole body or muscle tissues. In regard to aluminum content of the liver, whole body, and muscle tissues, detectable levels were not recorded. Based on these results, it does not appear that extremely high levels of aluminum or iron adversely affect juvenile red drum, and thus elevated levels of these minerals should not limit the use of algal coproducts in diet formulations.