Dietary xylooligosaccharide improved growth, nutrient utilization, gut microbiota and disease resistance of tilapia (Oreochromis niloticus x O. aureus)

Abstract

This study was conducted to examine the dietary effects of xylooligosaccharide (XOS) on growth, nutrient utilization, intestinal histology, microbial diversity and disease resistance of tilapia. A total of 375 fish (5.00 ± 0.02 g) were fed the five experimental diets containing XOS (95 % purity) at 0 (CON), 0.5 (X-1), 1 (X-2), 2 (X-3) and 4 (X-4) g/kg feed for 8 weeks. The weight gain (WG) and nutrient retention were significantly promoted, and feed conversion ratio (FCR) was decreased by dietary supplementation of XOS (P<0.05). The X-3 group (2 g/kg XOS addition) had the highest WG (1113.11 %) and the lowest FCR (0.97) among all the groups. The digestibility of dry matter was significantly enhanced by XOS supplementation at 2 g/kg (X-3 group) (P<0.05). The serum activities of alkaline phosphate (except X-1 group) and acid phosphatase (except X-4 group) were significantly increased by XOS supplementation, and the lysozyme activity was significantly enhanced in X-4 group (P<0.05). In liver, the superoxide dismutase activity was significantly improved in all XOS groups, and the catalase activity was significantly advanced in X-3 and X-4 groups (P<0.05). The protease (except X-4 group) and amylase activities were significantly promoted by XOS supplementation (P<0.05). The villus height of X-2, X-3, X-4 groups and muscular thickness of X-4 group were significantly higher than those of the control group (P<0.05), but the XOS supplementation presented lower villus width than the control group (P<0.05). The numbers of lactic acid bacteria and Bacillus were significantly enhanced in all XOS groups (P<0.05), and the number of Escherichia coli was decreased in X-3 and X-4 groups (P<0.05). Dietary XOS significantly reduced the cumulative mortality of tilapia after injected with Aeromonas hydrophila (P<0.05). In conclusion, the growth performance and health status of tilapia were promoted by dietary XOS, and the supplementation level was suggested to be 1−2 g/kg feed.