Effects of fructooligosaccharide on growth, immunity and intestinal microbiota of shrimp (Litopenaeus vannamei) fed diets with fish meal partially replaced by soybean meal

The effects of fructooligosaccharide (FOS) on growth performance, immunity and predominant autochthonous intestinal microbiota of shrimp (Litopenaeus vannamei) fed diets with fish meal (FM) partially replaced by soybean meal (SBM) were evaluated. After acclimation, shrimps (1.82 +/- 0.01 g/kg) were allocated into 15 tanks (25 shrimps per tank) and fed five different diets including positive control diet (C0, containing 250 g/kg FM and 285 g/kg SBM), control diet (C, containing 125 g/kg FM, 439 g/kg SBM) and three experimental diets supplemented with 1.0 g/kg FOS (T1), 2.0 g/kg FOS (T2) and 4.0 g/kg FOS (T3) to control diet (C) respectively. Shrimps were fed diets to apparent satiation three times per day, and 15 shrimps from each aquarium were randomly sampled and analysed at the end of the 6-week feeding trial. The results showed that FBW, WGR, SGR and SR decreased, while FCR and FI increased significantly in control (C) compared with positive control (C0). Besides, significantly decreased trypsase and lipase activities, and SOD, AKP and ACP activities were recorded in control (C) compared with positive control (C0). On the other hand, significantly improved SGR and decreased FCR were observed in groups T1, T2 and T3 compared with control (C). Moreover, lipase and amylase activities enhanced significantly in group T3 compared with the control (C), while GOT and GPT activities dropped significantly with the increment supplementation of FOS in diets. Compared with the control (C), SOD activity enhanced significantly and MDA level decreased significantly in groups T2 and T3, and improved AKP and ACP activities were observed in group T3. In addition, dietary FOS improved the microbial diversity, and suppressed several potential pathogens, such as Vibrio tubiashii, Vibrio parahaemolyticus and Photobacterium damselae-like strains in the intestine of shrimp. Overall, these results proved FOS could relieve the side effects induced by SBM and supported the use of 2.0-4.0 g/kg FOS in shrimp diets with FM partially replaced by SBM.