Effects of fish meal replaced by fermented soybean meal on growth performance, intestinal histology and microbiota of largemouth bass (Micropterus salmoides)

This study was conducted to investigate the effects of replacing fish meal (FM) with fermented soybean meal (FSM) and soybean meal (SM) on growth performance, intestinal histology and microbiota of largemouth bass (Micropterus salmoides). The basal diet contained 350 g/kg FM (CON), and then, FM was replaced with SM and FSM at the ratios of 30% and 60% (SM-30, SM-60, FSM-30 and FSM-60), respectively. The largemouth bass (4.43 +/- 0.13 g) were fed for 8 weeks. The results showed that weight gain of fish fed with FSM-60 and SM-60 diets was significantly lower, and feed conversion ratio of SM-30, SM-60 and FSM-60 groups was significantly higher than the CON group (p < .05). The intestinal villus height of SM-60 group and the villus width of SM-60 and FSM-60 group were significantly lower than the CON group (p < .05). The 30% FM replacement by SM and FSM significantly increased the abundance ofCetobacteriumandMycoplasma, respectively (p < .05). In conclusion, FSM could replace 30% FM in diet without negative impacts on the growth performance of largemouth bass, while the SM should be controlled below 30%.