Beneficial effects of oleanolic acid on hepatopancreas oxidative stress and intestinal microbiota structure of red swamp crayfish (Procambarus clarkia)

Abstract

This study aimed to evaluate the beneficial effects of oleanolic acid (OA) in the culture of red swamp crayfish (Procambarus clarkia) by investigating the impact of dietary OA on growth performance, hepatopancreas antioxidant activity, innate immunity, and intestinal microbiota structure. An eight-week feeding trial was conducted using different dietary OA concentrations: 0, 250, 500, 750, and 1000 mg·kg–1. The results revealed that the groups with 500–1000 mg·kg–1 OA exhibited increased final body weight, weight gain rate, and specific growth rate, as well as decreased feed conversion ratio compared to those in the control group (P < 0.05). Serum alanine transaminase (ALT) and aspartate transaminase (AST) activities showed a linear decrease with increasing dietary OA concentration. OA demonstrated hypolipidemic effects by reducing serum glucose, total cholesterol, triglyceride, and low-density lipoprotein cholesterol levels, while increasing serum high-density lipoprotein cholesterol levels (P < 0.05). OA500 to OA1000 groups exhibited significantly higher trypsin activity compared to that of the control, while lipase activity linearly decreased with increasing dietary OA concentration. The antioxidant capacity, as indicated by glutathione level in the hepatopancreas, showed significant differences between the OA treatment group and the control group. However, dietary OA did not significantly alter the structure of the intestinal microbiota. These findings suggest that dietary OA supplementation effectively improves the growth performance and enhanced the innate immunity of crayfish. Furthermore, OA significantly promotes the antioxidant capacity, thereby protecting the hepatopancreas from oxidative damage. The optimal dose range of dietary OA for application in crustacean culture is recommended to be between 500 and 1000 mg·kg−1.