The aim of this study was to evaluate the effects of prebiotics (mannanoligosaccharide and xylooligosaccharide), probiotics (Enterococcus faecalis and Pediococcus acidilactici) and synbiotics for 126 days on the immune responses, hemolymph indices, antioxidant enzymes and biological responses against 48-hr Aeromonas hydrophila exposure challenges of sub adult crayfish (11.45±1.87 g). The highest antibacterial activities were observed in shell mucus of crayfish fed with the diets containing xylooligosaccharide + E. faecalis and mannanoligosaccharide + Pediococcus acidilactici against Nocardia brasilience and Vibrio harveyi (p<0.05). Feeding crayfish with the xylooligosaccharide + E. faecalis - diet increased protein levels and the activities of alkaline phosphatase and lysozyme in shell mucus after feeding trial and 48-hr post A. hydrophila-injection challenge (p<0.05). The highest ratios of lactobacillus count to total viable count were observed in synbiotic diets (p<0.05). Feeding crayfish with xylooligosaccharide + E. faecalis – diet increased the specific growth rate and resistance against A. hydrophila-injection challenge (p<0.05). These results revealed that feeding crayfish with synbiotic diets was more effective than singular administration with prebiotics and probiotics.

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