The effects and mechanisms of dietary ferulic acid (FA) and dihydromyricetin (DMY) on growth and physiological responses of the shrimp (Litopenaeus vannamei)

The aim of this study was to comprehensively investigate the impact of ferulic acid (FA) or FA-dihydromyricetin (DMY) complex on the growth and physiological responses of Litopenaeus vannamei and their underlying mechanisms, as well as to examine whether the combined use of FA and DMY exhibits synergistic effects. A total of 1050 healthy shrimp were randomly allocated into 15 tanks, three tanks per group. The shrimp were provided with five different diets for 8 weeks. After different feeding experiments, a challenge test lasting for seven days was conducted using Vibrio parahaemolyticus (VP). The results of growth parameters showed that there were significant differences between all treatment groups and the control group in weight gain rate (WG), specific growth rate (SGR) and feed conversion ratio (FCR). Additionally, the hepatopancreas index (HSI) and condition factor (CF) were significantly increased in FD2 group. The activities of protease, lipase and amylase in hepatopancreas were significantly elevated in the FD1 group compared to the control group. Decreases in body crude fat content and plasma lipid parameters suggested that both FA and FA-DMY complex can reduce lipid deposition. Furthermore, dietary FA or FA-DMY complex could enhance lipid metabolism by regulating the expression of genes involved in fatty acid and triglyceride metabolism in hepatopancreas. Results of antioxidant capacity and immune responses indicated that the addition of FA or FA-DMY complex in the diet enhanced physiological responses in shrimp, as evidenced by increased antioxidant enzyme activities, elevated immune parameters, and upregulated the expression of immune-related genes in hemocytes and intestine. Additionally, dietary FA could improve intestinal health by modulating the composition and richness of intestinal microbiota. The results of the safety assessment showed that both FA and low-level FA-DMY complex had positive effects on the health status of hepatopancreas, but the dietary combination of FA and DMY (100 mg/kg + 200 mg/kg) could induce hepatopancreatic damage. In summary, dietary FA or FA-DMY complex has the potential to enhance the growth and physiological responses of L. vannamei. Moreover, the dietary combination of FA and DMY at appropriate levels had synergistic effects.