Abstract:Lipids, as essential substances in fish feed, provide important nutrients for fish growth and development, but they are easy to be oxidized, endangering the health of aquatic animals. As a good antioxidant, taurine has been widely studied for its effects on antioxidants and growth in fish, but its biological function on intestinal health needs to be further studied. To investigate the effects of taurine on the growth performance and intestinal health of Yellow River carp fed with a lipid-oxidized diet, we first replaced the fresh fish oil in the basal diet (FO) with the same amount of oxidized fish oil (OFO). Then, taurine with different concentrations (0.4%, 0.8%, and 1.2%) was added into the OFO diets (denoted as T0.4, T0.8, and T1.2, respectively) to cultivate the common carp with an initial body weight of (8.74 ± 0.01) g for 10 weeks. The results showed that final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR), and feed efficiency (FE) were significantly reduced in the OFO group compared with the FO group. All the above indexes in the T0.4, T0.8, and T1.2 groups were significantly higher than those in the OFO group. The mRNA expression levels of intestinal antioxidant enzymes showed that the expression of gr and gpx reached the highest level in the T0.8 group and was significantly higher than that in the OFO group. The expression level of the hepatopancreatic antioxidant gene showed that gr expression reached the lowest level in the OFO group, but increased in different levels of taurine groups. In addition, compared with the OFO group, the expression levels of sod and gpx were significantly increased in the T0.4 group, while the expression of keap1 was significantly decreased in the T0.8 and T1.2 groups. Intestinal digestive enzyme activity and histomorphological analysis showed that the intestinal digestive enzyme activities (lipase, amylase, and trypsin), villus height, villus width, and muscular thickness were significantly decreased in the OFO group compared with the FO group. At the same time, the above indexes in the experimental groups supplemented with taurine were higher than those in the OFO group. The alpha-diversity index of carp intestinal flora showed that the Observed species index and Simpson index of the OFO group were significantly lower than those of the FO group, and the Shannon index was significantly lower than that of the FO group. At the same time, compared with the OFO group, the Shannon index is significantly increased in the T0.8 group, and the Chao1 index is significantly increased in both the T0.8 and T1.2 groups. Further comparison of species composition in different experimental groups showed that the relative abundance of pathogenic bacteria (Aeromonasd and Acinetobacter, etc.) in the OFO group was significantly higher, and beneficial bacteria (Lactobacillus, Cetobacterium, and Prevotella, etc.) was significantly lower than that in FO group. However, compared with the OFO group, the content of intestinal pathogenic bacteria was decreased and the content of beneficial bacteria was increased in the taurine groups, and the effect was most significant in the T0.8 group. In conclusion, taurine alleviated the inhibition of growth, the damage to intestinal structure, the decline of digestive function, and the disturbance of intestinal flora caused by lipid oxidation feed on Yellow River carp. Combined with the results of this study, the recommended supplemental dosage of taurine in oxidized lipid diets is 0.4 % to 0.8 %. This study laid a theoretical foundation for further exploring the biological function of taurine in fish intestines.