Taurine alleviated the negative effects of lipid oxidation diet on growth performance and intestinal health of Yellow River carp (Cyprinus carpio)

Lipid oxidation is prevalent in fish feed, which reduces the nutritional value of fish feed and damages the health of aquatic animals. Taurine has been extensively studied as a feed additive to promote fish growth and antioxidant capacity, but its effects on intestinal health need further research. To investigate the effects of taurine on the growth performance and intestinal health of the Yellow River carp (Cyprinus carpio) fed with a lipid-oxidized diet, a total of 225 C. carpio with similar weight at about 8.74 g were randomly divided into five groups: FO, OFO, T0.4, T0.8, and T1.2, respectively. A 10-week feeding trial was performed. The results showed that taurine supplementation alleviated the growth inhibition caused by the OFO diet on C. carpio, mainly by improving final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR), and feed efficiency (FE). The oxidized lipid diet inhibited nrf2 mRNA expression in the hepatopancreas and intestine and promoted the mRNA levels of keap1 in the intestine. Appropriate taurine addition can inhibit the decrease of nrf2 mRNA levels and increase of keap1 mRNA levels induced by the OFO diet. Taurine also increased mRNA levels of antioxidation-related genes (gr, gpx and sod). For example, supplementation of 0.8 g/kg taurine significantly increased intestinal gr, gpx, and sod expression levels. In addition, taurine mitigated the decreased intestinal digestive enzyme activity (lipase, amylase, and trypsin), villus height, villus width, and muscular thickness of the oxidized lipid diet. Moreover, taurine restored the decreased alpha-diversity index (Chao1, observed species, Shannon, and Simpson index) of intestinal flora induced by the oxidized lipid diet. Furthermore, supplementation of 0.8% taurine reversed intestinal flora disturbance caused by the oxidized lipid diet, mainly by reducing the abundance of pathogenic bacteria (Aeromonasd and Acinetobacter, etc.) and increasing the abundance of beneficial bacteria (Lactobacillus, Cetobacterium, and Prevotella, etc.). In conclusion, taurine mitigated the negative effects of lipid oxidized diet on the growth performance and intestinal health of C. carpio, and the recommended supplemental level of taurine in the oxidized lipid diet was 0.4%–0.8%. This study lays a theoretical foundation for further exploring the biological function of taurine in fish intestines.