Combined effects of jujube, Chinese yam and astragalus on digestion, immunity and intestinal microflora of rainbow trout

Abstract

Jujube (Ziziphus jujuba mill.), Chinese yam (Dioscorea oppositifolia L.) and astragalus (Astragalus propinquus Schischkin) are important herbal medicines, which have several beneficial effects on host such as immunomodulation, antioxidant and gastrointestinal protection. In the study, the beneficial effects of dietary the above three herbal medicines compound supplementation on digestion and immunity of rainbow trout (Oncorhynchus mykiss) were studied. The fish were fed for 56 days with diets containing 0, 0.3%, 0.6% and 1.2% compound herbal medicines extract, and then gastrointestinal digestive enzyme activity, nonspecific immune genes expression and intestinal microbial diversity were tested. Pepsase activity in 0.3% and 0.6% groups, intestinal alpha-amylase activity in 0.3% group and erepsin activity in 0.6% and 1.2% groups were significantly improved (p < 0.01). The expression level of C3, IL-1 beta, IL-6 and HSP90BB genes in the spleen was significantly up-regulated in 0.6% group (p < 0.01). The expression of SOD in intestinal tissue increased in 0.6% group (p < 0.05), while TGF-beta was significantly down-regulated in 0.3% and 0.6% groups (p < 0.01). In the gut microflora, there were significant differences in the gut abundances of two phyla (Cyanobacteria and Patescibacteria) and two genera (A2 and Candidatus_Saccharimonas) among the four experiment groups (p < 0.05). Moreover, the clusters of orthologous groups and KEGG analysis showed that the compound herbal medicine may affect the intestinal digestion and immunity of rainbow trout. All of the above results showed that 6% compound herbal medicine added could promote the digestion, regulate the distribution of intestinal microflora and improve the nonspecific immune function of rainbow trout.