Effects of fermented feed on growth and digestive function of juvenile Chinese mitten crab, Eriocheir sinensis

Fermented feed has the functions of promoting animal growth, improving aquaculture water environment and meeting the nutritional needs of animals. It has been widely used in aquaculture currently. The hepatopancreas is crucial for digestion and absorption of Chinese mitten crab, Eriocheir sinensis. This study evaluated the effects of different proportions of fermented feed (0%, 10%, 20%, 30% and 40%) on the growth performance and digestion of E. sinensis. After a 60-day feeding period, the growth performance, digestive enzyme activities and expression levels of digestion-related genes of juvenile E. sinensis showed a tendency of first increasing and then decreasing, and were highest in 30% fermented feed group. The number of blister-like and fibrillar cells also increased in 30% fermented feed group. Furthermore, hepatopancreas microbiota and metabolomics analyses were conducted on 0% and 30% fermented feed. The results indicated that feeding with 30% fermented feed resulted in homeostasis of the hepatopancreas microbial community and upregulation of aminoacyl-tRNA biosynthesis, biosynthesis of amino acids, and tryptophan metabolism in 30% fermented feed group. Spearman correlation analysis revealed that several key differentially expressed metabolites were positively correlated with the presence of major bacterial genera following feeding with 30% fermented feed. These findings indicate that the intake of fermented feed may benefit hepatopancreatic physiological homeostasis in juvenile E. sinensis by enhancing growth performance and digestive and metabolic functions, and 30% fermented feed had the best effect on the growth and digestive function of juvenile E. sinensis.