The substitution of fish meal-soybean meal mixture with fermented soybean meal promoted the growth and intestinal health of yellow catfish (Pelteobagrus fulvidraco)

This study evaluated the potential of fermented soybean meal (FSBM) as substitute for fishmeal-soybean meal mixture (1:2) in diets of yellow catfish ( Pelteobagrus fulvidraco ). FSBM was incorporated into the basal diet (180 g/kg fishmeal, 200 g/kg soybean meal) at levels of 60, 120, 180, and 240 g/kg by replacing the corresponding fishmeal-soybean meal mixture, thereby formulating five diets as the CON (control), FSBM-6, FSBM-12, FSBM-18 and FSBM-24 groups. Then, the above five diets were used to feed yellow catfish (16.70 ± 0.23 g) in recirculating system for 8 weeks. The growth performance evaluation revealed a marked increase in weight gain (WG) and feed intake (FI) for the FSBM-6 relative to the CON ( P < 0.05). Serum total cholesterol (T-CHO) content, glutamate aminotransferase (AST) activity in the FSBM-6 group, and T-CHO, triglyceride (TG) content in the FSBM-12, FSBM-18, and FSBM-24 groups exhibited significant reductions in comparison with the CON ( P < 0.05). Moreover, serum glucose (GLU) content, total antioxidant capacity (T-AOC),and alanine aminotransferase (ALT) activity were significantly depressed in the FSBM-24 relative to the CON ( P < 0.05).The FSBM-6 and FSBM-12 groups displayed enhanced intestinal amylase activity relative to the CON ( P < 0.05), and the FSBM-18 and FSBM-24 groups demonstrated decreased diamine oxidase activity, and trypsin activity in the FSBM-24 was also considerably diminished ( P < 0.05). The FSBM-6 group showed a substantial elevation in anti-inflammatory factors ( tgf-β and il-10 ), while the FSBM-12 group displayed a divergent response, with downregulated tnf-β and upregulated tgf-β ( P < 0.05). In liver and gut histology, the FSBM-6, FSBM-12, and FSBM-24 groups showed significantly lower vacuolization rate of liver cell and higher muscularis thickness (MT) of intestine than the CON ( P < 0.05). In gut microbiota profile, the FSBM-6 and FSBM-24 groups exhibited significantly higher Simpson index, abundance of Fusobacteriota, and Cetobacterium, but a markedly reduced abundance of Pseudomonadota relative to the CON ( P < 0.05). Collectively, graded levels of FSBM (60-240 g/kg) improved serum biochemical indexes and intestinal health while growth performance was maintained, and the low replacement (60 g/kg) promoted the FI and WG of yellow catfish.