Replacing fish meal with fermented rice protein in diets for hybrid groupers (Epinephelus fuscoguttatus♀× Epinephelus lanceolatus♂): Effects on growth, digestive and absorption capacities, inflammatory-related gene expression, and intestinal microbiota

Abstract

A feeding trial was carried out to investigate the effects of dietary fermented rice protein (FRP) on growth, digestive and absorption capacities, inflammatory-related gene expression, and intestinal microbiota in juvenile hybrid groupers (Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂). A fish meal (FM)-based diet was used as a control for comparison with diets in which FM was replaced by FRP at percentages of 10 % (FRP10), 30 % (FRP30), and 50 % (FRP50). Each diet was fed to triplicate groups of fish for 56 days. We observed no significant differences in weight gain rate, specific growth rate, and protein productive value between the FM and FRP10 groups, but significantly lower rates in the FRP30 and FRP50 groups. The activities of the intestinal digestive enzymes (amylase, trypsin, and pepsin) and brush border enzymes (Na+/K+-ATPase, creatine kinase, and γ-glutamyl transpeptidase) were higher in the FRP-containing groups than in the FM group. The expression levels of immune-related genes (TLR22, MyD88, TNF-α, IL-2, IL-6, IL-8, and TGF-β1) were all down-regulated in FRP-fed fish. Intestinal microbiota showed no significant differences in alpha diversity among dietary groups. At the genus level, FRP-containing groups had lower relative abundances of Bacteroides and Enterococcus than the FM group. In conclusion, 10 % of the FM protein in the feed can be replaced by FRP without adverse effects on nutritional status. Replacing FM with FRP in the feed suppresses inflammatory function in hybrid groupers. It also has a critical influence on microbial profiles but not on diversity.