Dysbiosis of intestinal microbiota induced by dietary oxidized fish oil and recovery of diet-induced dysbiosis via taurine supplementation in rice field eel (Monopterus albus)

Intestinal microbiota plays crucial roles in host health. Unlike oxidized fish oil, taurine supplementation shows positive effects on intestinal health, whereas their impacts on intestinal microbiota remain unclear. Therefore, our goal of the present study was to understand the homeostasis mechanism and function of intestinal microbiota in rice field eel (Monopterus albus) fed with 5 experimental diets including basal diet (Control group), diets containing 100 (POV100 group) and 600 (POV600 group) meq/kg oxidized fish oil, and 600 meq/kg diet with supplementation of 0.1% (Tal group) and 0.2% (Ta2 group) taurine, respectively. Our results suggested that Clostridia, Fusobacteriia, and Gammaproteobacteria were three predominant microflora in the gut of eels. However, oxidized fish oil diet decreased the number of species and species richness together with a reduction in intestinal microbial diversity, and reduced the relative abundance of Clostridia caused by a significant increase in Fusobacteriia (classified as Cetobacterium). Nevertheless, 600 meq/kg oxidized fish oil diet with supplementation of taurine could reinstate the number of species and species richness, and the microbial diversity become higher compared to Control group. Oxidized fish oil induced microbial dysbiosis through the restriction of ecological network by declining the average connectivity and the total number of generalists, whereas taurine supplementation could reduce the negative impacts of oxidized fish oil and maintain the stability of intestinal microbiota. Furthermore, the increasing level of oxidized fish oil intensified the difference in microbial function from that in Control group, whereas 0.2% taurine supplementation restored its function to a similar level as that in Control group. These results suggested that the oxidized fish oil diet could disturb the stability of microbial community and cause microbial dysfunctions, whereas taurine supplementation helped the intestinal microbiota homeostasis and restored its function.