Dietary methionine hydroxy analogue supplementation benefits on growth, intestinal antioxidant status and microbiota in juvenile largemouth bass Micropterus salmoides

To study the possible impacts of dietary methionine hydroxy analogue (MHA) on growth, intestinal antioxidant status, and intestinal microbiota in juvenile largemouth bass (LMB) Micropterus salmoides (14.49-14.58 g), we conducted a feeding trial for 84-days. Four hundred and eighty fish were randomized into four dietary MHA treatments (0.0, 3.0, 6.0, and 9.0 g/kg diet). Results revealed that dietary MHA supplementation: (1) dramatically improved growth of juvenile LMB; (2) markedly decreased intestinal protein and lipid peroxidation, and increased intestinal antioxidant activities via Keap1/Nrf2 axis; (3) increased the richness and diversity of intestinal microbial community; (4) changed intestinal microbiota composition, increased the abundances of Proteobacteria, Bacteroidetes, and Actinobacteria, and decreased the abundances of Firmicutes and Cyanobacteria at the phylum level; increased the abundances of Bifidobacterium and Bacillus and decreased the abundance of Bacteroides at the genus level. Collectively, dietary MHA supplementation has potential benefits in growth, intestinal antioxidant capacity, and intestinal microbiota in LMB. The dietary optimal Met level of LMB (14.49-131.06 g) was recommended to be 14.49 g/kg diet, corresponding to 8.30 g/kg diet sourcing from basic diet and 4.19 g Met/kg diet sourcing from MHA based on specific growth rate.