Dietary supplementation of N-carbamylglutamate promotes growth performance by modulating the homeostasis of gut microbiota in tilapia (Oreochromis niloticus)

Abstract

N-carbamylglutamate (NCG) supplementation promotes the synthesis of arginine, improves physiological parameters and modulates gut function in fish. However, its beneficial effect on the fish gut microbiota remains unclear. Thus, we investigated the beneficial effect of NCG on homeostasis of gut microbiota in tilapia. Tilapia were fed with diets supplemented with different levels of dietary NCG (Ctrl, NCGI and NCGII) for 8 weeks. The weight gain and the specific growth rate were significantly higher (p < 0.05) in NCG-supplemented groups compared to the group Ctrl. Moreover, the V3-V4 region of 16S rDNA was sequenced, and the bioinformatic analysis suggested that dietary NCG supplementation had a limited impact on the α-diversity of gut microbiota, while Non-metric multidimensional scaling analysis (NMDS) showed that dietary NCG leads to a clear separation on gut microbiota among the three groups. Furthermore, NCG supplementation reshaped the tilapia gut microbiota community, according to co-occurrence analysis and metabolic pathways prediction via PICRUSt analysis, leading to an enrichment of nutritional metabolism related functions, such as amino acid and lipid metabolisms (p < 0.05). Subsequently, the redundancy analysis (RDA) demonstrated that the structural changes of gut microbiota were determined by NCG concentration. In addition, the linear discriminant analysis effect size (LEfSe) analysis revealed 65 differentially abundant taxonomic clades were dominant in tilapia supplemented with NCG. The cross-validation and Random Forest model identified 12 key bacterial taxa in response to the NCG supplementation. Among them, four key bacterial taxa played a fundamental role in nitrogen-fixing, which may indicate that NCG increases the amino acid biosynthesis of gut microbiota and contributes to the growth promotion of tilapia.