Inulin alleviates hypersaline-stress induced oxidative stress and dysbiosis of gut microbiota in Nile tilapia (Oreochromis niloticus)

This study explored the alleviation of salinity-induced stress by adding dietary prebiotic inulin in Nile tilapia Oreochromis niloticus. Tilapias were administrated with four levels of inulin (0, 0.2%, 0.4% and 0.8%) at the salinity of 16 psu (practical salinity unit) for 8 weeks, and meanwhile the tilapia fed the basal diet in freshwater were served as a freshwater control. The final weight, weight gain, and specific growth rate increased but feed conversion ratio decreased in the 16 psu group compared to the freshwater group. These trends became more evident in groups of 16 psu + 0.2% inulin and 16 psu + 0.4% inulin, and the best growth was obtained in the 16 psu + 0.4% inulin group. SOD activity was significantly elevated while CAT and GST activities were markedly reduced in 16 psu group compared to the freshwater group, but these parameters returned to the freshwater group level when tilapia were fed with 0.4% inulin. Amylase and protease activities were significantly increased in 16 psu group compared to the freshwater group, but reduced and returned to the level of freshwater group by adding 0.2% and 0.4% inulin to the diet. The composition, α-diversity, and β-diversity of gut microbiota were disturbed in 16 psu group, but returned to the freshwater group pattern in 16 psu + 0.8% inulin group. The results show that dietary inulin is an effective feed additive to alleviate the oxidative stress and gut microbiota dysbiosis at 16 psu. This study suggests that dietary manipulation using inulin is a promising strategy to improve fish healthy under saline stress, and the optimal level of inulin supplementation to the diet is 0.4% for Nile tilapia at 16 psu.