Evaluation of spent mushroom substrate extracts from Cordyceps militaris: Impact on growth Performance, Immunomodulation, and intestinal microbiota of Nile tilapia

• Methanolic SMS extraction yielded significant concentrations of cordycepin (3,570 µg/g) and adenosine (170 µg/g). • SMS extract boosted Nile tilapia immunity, raising WBC and RBA values, but did not significantly enhance growth. • SMS extract enhanced the survival of pathogen-infected Nile tilapia, suggesting potential applications in disease resistance. • Nile tilapia's intestinal microbiota showed shifts in probiotics and pathogens, providing insights to improve aquaculture practices. The spent mushroom substrate (SMS) of Cordyceps militaris , often discarded from commercial cultivation, contains valuable bioactive compounds like cordycepin and adenosine. This study explored the extraction and use of SMS extract in Nile tilapia diets, revealing concentrations of 3,570 ± 25.0 µg/g of cordycepin and 170 ± 7.4 µg/g of adenosine in the methanolic extract. Nile tilapia were fed diets supplemented with SMS extracts at 10, 15, and 20 mg/kg for 8 weeks. There were no significant improvements in performance or feed utilization compared to the control group. The SMS extract at 20 mg/kg significantly improved immunity, with a twofold increase in white blood cell (WBC) counts, higher respiratory burst activity (RBA), and lower mortality rates from Aeromonas hydrophila and Streptococcus agalactiae infections. Shifts in intestinal microbiota were also observed, reflecting a complex interaction between SMS extracts and fish health. Our results indicated that administering SMS extracts at an optimal dosage of 20 mg/kg enhanced immunity, promoted disease resistance, and increased intestinal probiotics in Nile tilapia. These findings demonstrate the potential of SMS extracts in aquaculture. However, more research is necessary to comprehensively understand how SMS extracts can boost fish health and production.