Influence of diet shift from bloodworm to formulated feed on growth performance, gut microbiota structure and function in early juvenile stages of hybrid sturgeon (Acipenser baerii × Acipenser schrenckii)

Currently sturgeon farming is one of the common cold fresh water farming in China, but its production is very low comparing with the country's cold water fish farming potential. One of the main reasons for the low production of sturgeon is unavailability of proper feed for early live stage of sturgeon. The aim of this study was to examine the effects of diet shift from live food (bloodworm) to formulated feed on growth performance, structure and function of gut microbiota in early juvenile stages of hybrid sturgeon (Acipenser baerii × Acipenser schrenckii). Significantly increased in weight gain rate (WGR) and feed conversion ratio (FCR) were observed in the sturgeon group fed on the formulated versus the bloodworm group (p < 0.05). Significantly higher Proteobacteria was recorded in the formulated feed group (p < 0.05), while Fusobacteria was significantly increased in the bloodworm group (p < 0.05). Furthermore, effects of colonization of the gut microbiota isolated from each group of sturgeon on host immunity was evaluated using germ free (GF) zebrafish model. The expression of genes related to anti-inflammatory (IL-10, TGF-β), non-specific immune (Lysozyme, C3a), and anti-virus (IFNΦ3, Mxb, Mxc) were significantly decreased in GF zebrafish colonized with gut microbiota of sturgeon fed on formulated feed, while expression of pro-inflammatory gene (TNFα) was significantly increased in formulated feed group. Moreover, GF zebrafish colonized with gut microbiota of sturgeon fed on the formulated feed revealed significantly lower survival rate for A. veronii Hm091 challenge (p < 0.05). In conclusion, the present study revealed that, compared with bloodworm, the formulated feed enhanced the WGR and FCR of sturgeon, but induced intestinal microbiota dysbiosis, which negatively affected the immune response of GF zebrafish and decreased their resistance to pathogenic bacteria.