Effects of Dietary Alpinia officinarum Extract on Performance, Immunity, Microbiota, and Aeromonas hydrophila Resistance in Red Claw Crayfish

Plant extracts contain multiple bioactive compounds and have been extensively investigated as alternatives to antibiotic-based feed additives in aquaculture. The present study was designed to evaluate the effects of dietary supplementation with galangal (Alpinia officinarum) extract (AO) on the growth, immune response, intestinal digestive enzyme activities, gut microbiota, and resistance to A. hydrophila in red claw crayfish (Cherax quadricarinatus). Crayfish with an initial body weight of 0.83 ± 0.05 g were randomly assigned to 18 tanks (6 groups × 3 replicates) and were fed basal diets supplemented with 0, 0.5, 1, 3, 5, or 7 g/kg of AO for 8 weeks. The weight gain rate (WGR) and specific growth rate (SGR) of crayfish were significantly higher in the 3 g/kg and 5 g/kg groups than in the control group. Dietary supplementation with 3–5 g/kg AO significantly elevated the crude protein content and reduced the crude lipid content in the muscle. AO supplementation at 3–5 g/kg significantly enhanced the total antioxidant capacity (T-AOC) and the activities of glutathione peroxidase (GPx), catalase (CAT), acid phosphatase (ACP), and phenol oxidase (PO), whereas the content of malondialdehyde (MDA) was significantly reduced. Dietary AO supplementation markedly increased the relative abundance of Firmicutes, Cytophaga, and norank_o_Saccharimonadales. Moreover, dietary AO significantly upregulated the expression of multiple functional genes in the hepatopancreas, including ecCu, Zn-SOD, Trx1, ALF, C-LZM, GPx, and Se-GPx, and improved the survival of the C. quadricarinatus under challenge with A. hydrophila. Collectively, the findings of the present study indicate that dietary supplementation with 3–5 g/kg AO enhances the growth performance, intestinal digestive enzyme activities, immune function, and disease resistance in the red claw crayfish (C. quadricarinatus).