There appears to be a close correlation between intestinal microbiotas and obesity. Still, our understanding of the relationship between the intestinal microbiota and body-mass in grass carp (Ctenopharyngodon idella) remains limited. Herein, we explored this association in the anterior, middle, and posterior intestine of cohabitating grass carp by using next-generation sequencing of the 16S rRNA gene. The results showed that alpha diversity indices of the low-weight-gain (LWG) groups were higher than that of the high-weight-gain (HWG) groups. HWG groups possessed the decreased ratio of Bacteroidetes to Firmicutes compared with that in the LWG groups. Principal coordinate analysis (PCoA) and analysis of similarities (ANOSIM) revealed that there were significant differences between the HWG and LWG groups. Furthermore, linear discriminant analysis (LDA) coupled with effect size (LEfSe) showed that the order Clostridiales were significantly abundant in the HWG groups. Phylogenetic molecular ecology networks (pMENs) showed a lower average path distance (GD), higher average clustering coefficient (avgCC), and higher average degree (avgK) in the HWG group. Our results suggested that there appeared to be a tight correlation between the intestinal microbiota and body-mass in grass carp. The study provides a referable resource for establishing the relationship between intestinal microbiotas and economic traits, which also lays a foundation for the progress of new fish probiotic in the future.

肠道菌群与肥胖之间似乎存在着密切的关系。尽管如此，我们对草鱼肠道微生物群与体质量之间关系的理解（Ctenopharyngodon idella）仍然有限。本文中，我们通过使用16S rRNA基因的下一代测序探索了在同居草鱼的前肠，中肠和后肠中的这种关联。结果表明，低体重（LWG）组的α多样性指数高于高体重（HWG）组。与LWG组相比，HWG组的拟杆菌与硬毛虫比率降低。主坐标分析（PCoA）和相似性分析（ANOSIM）显示，HWG和LWG组之间存在显着差异。此外，线性判别分析（LDA）加上效应量（LEfSe）显示梭状芽胞杆菌在HWG组中非常丰富。系统发育分子生态网络（pMENs）在HWG组中显示出较低的平均路径距离（GD），较高的平均聚类系数（avgCC）和较高的平均程度（avgK）。我们的结果表明草鱼的肠道菌群与体重之间存在紧密的联系。该研究为建立肠道菌群与经济性状之间的联系提供了参考资源，也为今后新型鱼类益生菌的发展奠定了基础。