Effect of taurine on intestinal microbes and immune function in golden pompano (Trachinotus ovatus)

In order to investigate the effects of taurine on the intestinal microflora structure and immune function of Trachinotus ovatus, we used fish meal, fermented soybean meal and corn gluten meal as the basic protein sources to prepare the nitrogen and fat feed with taurine contents of 1.3 g·kg⁻¹ (T0), 4.4 g·kg⁻¹ (T1), 7.4 g·kg⁻¹ (T2), 10.5 g·kg⁻¹ (T3), 12.7 g·kg⁻¹ (T4), respectively. Seven hundred and fifty individuals of T. ovatus with an average body mass of (80.0±0.5) g were randomly devided into five groups with three replicates of fifty fish, and the experiment lasted 56 d. Sequencing results show that a total of 87 707 sequences had been obtained in the intestine of T. ovatus. The number of OTUs that can be annotated to the database was 5 130 (95.32%). At phylum level, Proteobacteria, Tenericutes and Spirochaetes were the predominant phyla. Alpha diversity and beta diversity analyses show that the richness and diversity of intestinal microbial in T2 group were the lowest and the species composition was significantly different between T1 and T4 groups (P<0.05). The serum lysozyme activity, C4, and Ig increased significantly with the addition of exogenous taurine (P<0.05). The expression of ToTLR-1, ToTLR-2, ToTNF-α and ToIL-1β in each group decreased significantly (P<0.05). The expression of ToNFkB P65 of T1, T2 and T4 groups was significantly lower than that of the control group (P<0.05), while the expression of ToIL-10 of T3 and T4 groups was significantly higher than that of control group (P<0.05). The results indicate that exogenous taurine has a significant impact on intestinal microflora and immune function.