Abstract

This study aimed to evaluate the effects of using red fish meal (PRF, Peruvian red fish meal) and four types of white fish meal (NZWF, New Zealand white fish meal; NPWF, North Pacific white fish meal; RWF, Russian white fish meal; DWF, Danish white fish meal) as dietary protein sources on the growth performance, serum biochemical indices, intestinal histomorphology, antioxidant capacity, immune response, expression of genes related to the physical barrier, and gut microbial community in rice field eel ( Monopterus albus ), in order to identify the optimal fish meal type. Compared to the PRF group, the white fish meal groups showed significantly increased final mean body weight and condition factor. Serum levels of TG, TC, and BUN decreased significantly, while levels of GLU, IgM, and IgA increased significantly. Histological examination of the intestine revealed increased villus height and goblet cell density in the white fish meal groups. Furthermore, the white fish meal groups upregulated intestinal expression levels of nrf2 , sod , cat , gpx1 , tgf-β1 , zo-1 , zo-2 , cl-12 , cl-15 , and occ , and downregulated expression levels of il-1β , il-8 , nf-κb , and tlr-3 . Gut microbiota analysis revealed that the abundance of Bacteroidota was higher in the white fish meal groups than in the PRF group (>70% vs ∼50%), with significant enrichment of Muribaculaceae and Bacteroides . Network modules 1 and 2 showed strong positive correlations with growth/immune indices. Differential abundance heatmap analysis showed that NPWF and NZWF clustered into a healthy cluster, while PRF formed a separate cluster. White fish meals are superior to red fish meal, with NPWF demonstrating the best overall performance in terms of growth, metabolism, intestinal barrier function, immune regulation, antioxidant capacity, and beneficial bacterial network.