The antistress compound A outperforms others in boosting growth, antioxidant defence, and resilience to multiple stresses in largemouth bass

The sustainability of Micropterus salmoides (largemouth bass) aquaculture is challenged by environmental stressors, prompting this study to investigate the antistress compounds Antistress Fish and antistress compounds A and B (AscA and AscB) through a two-phase experimental design. In the initial 30-day feeding trial, the effects on growth, antioxidant capacity, and immune function were evaluated. Subsequently, stress resistance was assessed through controlled challenges, including high temperature, hypoxia, simulated transport, and pathogen exposure. Results demonstrated that dietary AscA significantly enhanced growth performance, as evidenced by higher weight gain rate, specific growth rate, and average daily gain, along with a reduced feed conversion ratio, compared to the other groups. Both AscA and AscB supplementation increased serum and hepatic activities of alkaline phosphatase (AKP), total antioxidant capacity (T-AOC), lysozyme (LZM), superoxide dismutase (SOD), and acetylcholinesterase (AChE), while reducing malondialdehyde levels compared to the control group (NC). Hepatic analyses further revealed a significant up-regulation in the expression of immune-related genes (Cu/Zn SOD, LZM, immunoglobulin M [IgM]) and a down-regulation of stress biomarkers (heat shock protein 70, interleukin [IL]-8, IL-1β) in AscA-fed fish. Following exposure to multiple stress challenges-including high temperature, hypoxia, simulated transport, and Aeromonas veronii infection-the AscA group exhibited significantly elevated serum activities of AKP, T-AOC, SOD, LZM, and AChE, as well as increased hepatic activities of AKP, SOD, LZM, and corresponding gene (Cu/Zn SOD, LZM, IgM) expressions compared to the NC group. Notably, AscA supplementation resulted in the highest survival rates following hypoxia and pathogen challenges, outperforming all other treatments. These findings indicate that dietary AscA and AscB enhance antioxidant capacity, immune responses, and resilience to multiple stressors in largemouth bass, with AscA demonstrating superior efficacy in mitigating aquaculture-related stress.