Effects of dietary administration of inosine on growth, immune response, oxidative stress and gut morphology of juvenile amberjack, Seriola dumerili

A 50-day feeding trial was conducted to determine the effects of dietary inosine on growth performance, immune responses, oxidative stress and gut morphology of juvenile amberjack, Seriola dumerili. Five isonitrogenous (52% crude protein) and isolipidic (14% crude lipid) semi-purified test diets were prepared by supplementing incremental levels of dietary inosine nucleoside at 0% (D1, control), 0.1% (D2), 0.3% (D3), 0.6% (D4) and 0.9% (D5), respectively. Triplicate groups of juvenile with an initial average weight of approximately 26 g were randomly stocked in fifteen, 200L polycarbonate tanks at a stocking density of 20 fish per tank. The fish were hand-fed twice daily to apparent satiation level. At the end of the feeding trial, final body weight (g), weight gain (%) and specific growth rate (% day− 1) were significantly (P < 0.05) higher in fish fed with D4 and D5 diets compared to those in D1 group. Significantly higher survival rate was found in D4, lowest in D1 and no differences were found between D4 and D5, respectively. Inosine supplemented groups showed significantly higher values of whole body lipid and hepatosomatic index compared to those in D1 group. Dietary inosine reduced the oxidative stress of fish. Lysozyme activity, bactericidal activity and peroxidase activity had increasing trends with the increasing levels of inosine in diets. On intestinal health condition, anterior enterocyte height was higher in D3, and anterior as well as posterior fold heights were also higher in inosine supplemented groups than D1 group. The quadratic regression analysis of weight gain and lysozyme activity revealed that the optimal levels of dietary inosine were 0.54 and 0.67%, respectively, for juvenile amberjack, which is also inline with the most of the growth performance and health parameters of fish under present experimental condition.