Dietary optimum inclusion level of jack mackerel meal for olive flounder (Paralichthys olivaceus, Temminck & Schlegel, 1846)

Abstract

Feed stimulants are used to incite feeding behavior in fish to improve feed consumption and growth. This study investigated the effect of jack mackerel meal (JM) as dietary attractant and/or stimulants on olive flounder on growth, feed utilization, chemical composition, plasma chemistry, and non-specific immune responses. In addition, the attractiveness of the experimental diets containing various levels of JM to olive flounder was evaluated. Six hundred and seventy five juveniles were randomly assigned to 27 tanks each containing 25 fish [initial weight of 5.3 ± 0.01 g (SEM)] in the 8-week feeding trial. The control diet (JM0) contains 60% fish meal (FM). The graded levels (1, 3, 5, 20, 20, 40, 60, and 100%) of JM were included at the expenses of FM, referred to as the JM1, JM3, JM5, JM10, JM20, JM40, JM60, and JM100 diets, respectively. Fish were hand-fed to visual satiation in triplicate groups of each diet twice daily for 8 weeks. To determine the attractiveness of the experimental diets, thirty fish were confined in the acclimatization chamber at a time and a knockout comparison of the experimental diets was applied. The strongest feeding attractant response of olive flounder was observed in the JM60 diet. Attractiveness of fish to the JM40 diet was also higher than that of fish to the JM20 diets. Weight gain and SGR of fish fed the JM20 diet was significantly (P < 0.0001) greater than those of fish fed the JM0, JM1, JM3, JM5, JM10, and JM100 diets, but not significantly (P > 0.05) different from those of fish fed the JM40 and JM60 diets in the 8-week feeding trial. The highest feed consumption was obtained in fish fed the JM20 diet. None of the organosomatic indices (condition factor, and viscerosomatic and hepatosomatic indices), biochemical parameters, non-specific immune responses (superoxide dismutase and lysozyme activities), chemical composition and amino acid and fatty acid profiles of the fish whole-body were affected by the experimental diets. In conclusion, the strongest attractiveness of fish was observed in the JM60 diet, but the optimal inclusion level of JM in the diets seemed to be 20% for juvenile olive flounder.