Effects of Supplemental Amino Acid‐Chelated Trace Elements on the Immune Response of Rainbow Trout Subjected to Bacterial Challenge

This study examined whether supplemental amino acid‐chelated trace elements were effective in improving disease resistance in rainbow trout Oncorhynchus mykiss. Four semipurified diets containing trace elements from either sulfates or an amino acid chelate source were fed to the fish for 18 weeks. Subsequently, fish weighing about 20–40 g were challenged with β‐hemolytic Streptococcus sp. The cumulative mortality was less in the chelate‐supplemented groups but not significantly different from that of the sulfate groups. Antibody titer was significantly higher in the chelate‐fed fish. Lysozyme activity and total immunoglobulin content were slightly more enhanced in the chelate‐fed than in the sulfate‐fed groups. Despite the increased antibody production, no distinct improvement in disease resistance against Streptococcus sp. was achieved by supplementing rainbow trout diets with amino acid‐chelated trace elements. Further confirmatory studies focusing on the amounts of the trace elements used are needed to shed light on the influence of amino acid chelates on disease resistance.