Yam (Rhizoma Dioscoreae) polysaccharide affects growth performance, immunity, and intestinal microbial community in Bulatmai barbel (LucioBarbus capito)

Polysaccharides from yam (Rhizoma Dioscoreae) can be used as immunopotentiators in aquaculture; however, the protective mechanism of adding them to feed for Bulatmai barbel (LucioBarbus capito) remains unclear. This study aimed to investigate the effects of adding yam polysaccharide (YP) to feed for 8 weeks on the growth performance, antioxidant capacity, gene expression, and intestinal flora of the Bulatmai barbel. The experimental groups were fed a diet including 0.1 %, 0.2 %, 0.4 %, and 0.8 % YP, whereas the diet of the control group contained no added YP, with three replicates per group. The results showed that the addition of YP significantly increased the weight gain rate and specific growth rate of the Bulatmai barbel, which were significantly higher than those of the control group (P < 0.05). The growth effect of the 0.4 % YP (279.77 ± 17.43 g) experimental group was significantly better than that of the other experimental groups, and the feed coefficient (49.35 ± 4.67 g) was significantly lower than that of the control group (P < 0.05). The addition of YP significantly improved immune activity and antioxidant capacity of the liver; HSP70 expression decreased and AKP and SOD expression levels significantly increased in the 0.40 % YP group (P < 0.05). In addition, the relative abundance of intestinal bacteria increased for Fusobacteriota and Firmicutes but decreased in Proteobacteria in the experimental groups compared with the control group. At the genus level, Cetobacterium was the dominant bacterium. With an increase in YP concentration, the relative abundance of Cetobacterium increased, whereas that of Pseudomonas and Phreatobacter decreased. In conclusion, dietary supplementation with 0.4 % YP significantly improved growth performance, antioxidant capacity, and gene expression; and regulated intestinal microbial diversity and floral structure in the Bulatmai barbel.