牛磺酸缓解脂质氧化日粮对黄河鲤生长性能和肠道健康的负面影响

为了探究牛磺酸对脂质氧化饲料饲喂下黄河鲤生长性能和肠道健康的影响，实验先用等量的氧化鱼油（记为OFO）替换基础日粮（记为FO）中的新鲜鱼油，接着将不同含量（0.4%、0.8% 和1.2%）的牛磺酸分别加入OFO组饲料中（分别记为T0.4、T0.8和T1.2），对初始体重为（8.74±0.01）g的黄河鲤进行为期10周的养殖实验。结果显示，与FO组相比，OFO组的终末体质量、增重率、特定增长率和饲料效率均显著降低。上述所有指标在T0.4、T0.8和T1.2组中均显著高于OFO组。另外，OFO组中肝胰脏抗氧化酶的mRNA表达水平显著低于FO组，而牛磺酸添加组中肝胰脏和肠道的抗氧化酶mRNA表达均有不同程度的上调。与FO组相比，OFO组中的肠道消化酶活性，肠绒毛高度、肠绒毛宽度和肌层厚度均显著降低，而在牛磺酸添加组中均得到提高。同样的，OFO组中肠道微生物组成的丰富度和多样性显著降低，条件致病菌丰度明显升高，而有益菌的丰度却有所下降，这些不良现象在牛磺酸组中均得到明显改善。研究表明，牛磺酸可缓解脂质氧化饲料对黄河鲤造成的生长性能抑制、肠道组织结构破坏、消化功能下降及肠道菌群紊乱等不良影响。结合本研究结果，在氧化脂质饲料中牛磺酸的建议添加剂量为0.4~0.8%。本研究为进一步探索牛磺酸对鱼类肠道的生物学功能奠定理论基础。

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

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.