Synbiotic effects of β-glucan, mannan oligosaccharide and Lactobacillus casei on growth performance, intestine enzymes activities, immune-hematological parameters and immune-related gene expression in common carp, Cyprinus carpio: An experimental infection with Aeromonas hydrophila

Abstract A feeding trial was conducted to determine the effect of dietary administration of β- glucan, mannan oligosaccharide (MOS) and Lactobacillus casei on growth performance, immune responses and disease resistance of Cyprinus carpio . To address that, 300 fish weighing 65 ± 5 g were divided into five treatments, including diet A: 0.5% β-glucan and MOS + 5 × 10 7  CFU L. casei kg −1 diet, B: 1% β-glucan and MOS + 5 × 10 7  CFU L. casei kg −1 diet, C 1.5% β-glucan and MOS + 5 × 10 7  CFU L. casei kg −1 diet, D: 5 × 10 7  CFU L. casei kg −1 diet and a control diet for 60 days and a subsequent 15 days as a cessation period. Results showed that supplementary diets and feeding period caused an increase in hematological parameters, serum lysozyme and complement activities whilst feeding cessation reduced them. Growth performance and feed utilization were enhanced especially following treatment B. In addition, intestine enzyme activities including, ALP, lipase, amylase, trypsin and protease were elevated significantly during the experimental period when compared with the control at the beginning of experiment. The kidney TNFα gene expression showed a significant increase. When all fed groups were subjected to a challenge test with Aeromonas hydrophila , lower mortality rate was observed in treatment B. The results suggest that these treatments, especially treatment B can improve C. carpio health status.