Effects of Chinese yam ( Dioscorea oppositifolia L .) dietary supplementation on intestinal microflora, digestive enzyme activity and immunity in rainbow trout ( Oncorhynchus mykiss )

Abstract

Chinese yam (Dioscorea oppositifolia L.) extract is a product which concentrates many active ingredients. In this study, the effects of Chinese yam extract on the intestinal microbiota, digestive enzymes, and the immune response of rainbow trout (Oncorhynchus mykiss) were investigated. Fish were fed a basic diet (Con) and 0.1% (O1), 0.2% (O2) and 0.4% (O3) yam extract diet, respectively, for 8 weeks. After the feeding experiment, Actinobacteria, Firmicutes and Patescibacteria abundances at the phylum level in intestinal were significantly differential under the effect of yam respectively. Actinobacteria and Firmicutes phylum were significantly decreased in O1 group compared with control, while Patescibacteria was significantly increased in O3 group. Anaeroplasma, Candidatus_Saccharimonas, Ruminococcaceae_ UCG-014, Lactobacillus, Rikenella, Lachnospiraceae_NK4A136_group, [Eubacterium]_ coprostanoligenes_group, Bifidobacterium, Marvinbryantia and Uncultured abundances at the genus level were significantly differential under the effect of yam respectively. Bifidobacterium, Marvinbryantia and Candidatus_ Saccharimonas were significantly enriched in O3 group. KEGG and COG functional prediction on intestinal microflora revealed that yam has beneficial effects on metabolism, antibacterial and defence function. Serum immune factors and intestinal immune genes were significantly regulated in yam groups. In addition, yam also increased gastrointestinal digestive enzyme activities of rainbow trout. The results showed that yam could enhance gastrointestinal function, stimulate immunomodulatory effects, and induce intestinal microbiota changes, rendering beneficial effects to rainbow trout.