Modulation of growth performance,haemato-immunological parameters, gut microbiota and stress resistance upon feeding juvenile Schizothorax zarudnyi (Nikolskii, 1897) by fructo-oligosaccharid

A 63-day experiment was carried out under controlled conditions to compare the effects of fructo-oligosaccharide (FOS) at four levels (5, 10, 20 and 30 g/kg) on growth performance, nutritional efficiency indices, haemato-immunological parameters, stress resistance, digestive enzymes and cultivable autochthonous intestinal microbiotaof juvenile (68.52 ± 1.52 g) Khaju fish Schizothorax zarudnyi. Fish fed the diet containing 20 g/kg FOS had significantly (p < 0.05) higher weight. Dietary FOS supplementation (5-20 g/kg) showed significant effects on SGR compared with control treatment. Hb, Haematocrit, MCV, MCH and lymphocytes in fish fed with the diet containing 20-30g/kg FOS were significantly higher than those in fish fed with control treatment. After 63-day feeding feeding period and also, 5-min air exposure challenge test, the activities of IG, LYZ and ACP in serum of fish fed with the diet containing 10-30 g/kg FOS showed a significantly higher trend than other treatments. The ratio of lactobacillus count to total autochthonous intestinal microbiota in fish fed with 10-30 g/kg FOS was significantly higher than that in other treatment groups. Furthermore, dietary FOS supplementation significantly increased survival rate of juvenile Khaju fish. Polynomial regression of SGR, FCR, PPV and PER suggested that the optimum dietary FOS level could be higher than 18.2 and < 23.8 g/kg in fish reared in culture conditions. These results indicate the beneficial effects of FOS, and emphasizes the need for further research to analyze the use of prebiotics on growth performance of fish