Effects of β-1,3-glucan feed supplementation on the growth, liver biochemistry, transcript levels and intestinal microorganisms of swamp eel (Monopterus albus)

This study investigated the effects of β-1,3-glucan feed supplementation on the growth, liver biochemistry, transcript levels, and intestinal microbiome of Monopterus albus . The experiment involved five groups: 0 % (CT), 0.2 % curdlan (EG-1), 0.1 % β-1,3-glucan (EG-2), 0.2 % β-1,3-glucan (EG-3), and 0.5 % β-1,3-glucan (EG-4). Monopterus albus were reared for 56 days, the final body weight, weight gain rate, survival rate, and specific growth rate were significantly increased, while the feed conversion rate was reduced considerably, in EG-2, EG-3, and EG-4 compared with the CT ( P < 0.05). The addition of β-1,3-glucan significantly reduced the malondialdehyde content ( P < 0.05), and significantly increased the activities of superoxide dismutase, catalase, and glutathione peroxidase in the liver ( P < 0.05). This indicated that β-1,3-glucan can effectively promote the growth and antioxidant capacity of M. albus . The results of liver tissue sections showed that β-1,3-glucan effectively reduced lipid accumulation in the liver. Transcriptome sequencing revealed that differentially expressed genes were significantly enriched in the peroxisome proliferator-activated receptor signaling pathway, indicating that β-1,3-glucan can regulate liver metabolic functions of M. albus . In addition, intestinal microbial assays showed that dietary β-1,3-glucan decreased intestinal microbial abundance and diversity. These results suggest that the β-1,3-glucan used in this study may reduce microbial abundance and diversity, potentially through the inhibition of certain harmful bacterial species. Furthermore, it increased the relative abundance of the beneficial bacteria Shewanella xiamenensis and the Lachnospiraceae NK4A136 group, which can alter intestinal microbial composition and maintain intestinal health. In summary, these results further elucidate the effects of β-1,3-glucan on the growth, liver antioxidant function and lipid metabolism, and intestinal microorganisms of M. albus . They can facilitate molecular mechanism analysis for the research and development of aquafeed functional additives, which is of great importance for the promotion of green and sustainable aquaculture. • β-1,3-glucan boosts growth and feed efficiency in Monopterus albus . • Enhances liver antioxidants, reduces lipid peroxidation. • Regulates PPAR pathways to lower hepatic lipid accumulation. • Gut microbiota restructured with beneficial bacteria for health.