Dietary sodium butyrate and poly-β-hydroxybutyrate improve growth performance, intestinal antioxidant and non-specific immune functions and resilience from ammonia stress in grass carp (Ctenopharyngodon idella)

To investigate the effects of butyrate supplementation on ammonia nitrogen stress resistance and intestinal recovery in grass carp (Ctenopharyngodon idella), fish were fed four experimental diets: control (CK), powdered sodium butyrate (PSB), microencapsulated sodium butyrate (MSB), and poly-β-hydroxybutyrate (PHB) at 600 mg/kg for 56 days. Following exposure to ammonia nitrogen (10.47 ± 0.67 mg/L) for 96 h and a 15-day recovery periods, results showed that PSB, MSB, and PHB significantly improved weight gain rate and specific growth rate. These supplements upregulated intestinal immune and antioxidant indices, including acid phosphatase (ACP), lysozyme (LZM), total superoxide dismutase (T-SOD), total antioxidant capacity (T-AOC), and β defensin (β − DF), while interleukin-1β (IL-1β) and malondialdehyde (MDA) levels decreased. During ammonia stress and recovery, these additives reduced oxidative damage (lower MDA), maintained antioxidant capacity (higher T-SOD/T-AOC), enhanced intestinal immune parameters (higher ACP/LZM activities and β − DF content), and exerted beneficial effects against ammonia-induced inflammation (lower IL-1β). Integrated biomarker response (IBR) analysis ranked MSB as the most effective treatment. Our findings demonstrate that dietary sodium butyrate and PHB supplementation enhances intestinal resilience against ammonia in grass carp.

Graphical abstract