From environmental stress to immune precision: A dual-strategy approach to antibiotic-free aquaculture

This study investigated the immunomodulatory effects of dietary supplementation with natural astaxanthin from Haematococcus pluvialis under biofloc culture conditions on the giant freshwater prawn (Macrobrachium rosenbergii). Prawns (42.0 ± 2.0 g) were reared for six weeks in four treatments: (1) clear water with basal feed (control), (2) biofloc with basal feed, (3) biofloc with 150 mg/kg astaxanthin, and (4) biofloc with 300 mg/kg astaxanthin. Immune responses were assessed by hemocyte profiling, lysozyme activity, phagocytic capacity, respiratory burst, and superoxide dismutase activity. Challenge experiments with Aeromonas hydrophila, Vibrio parahaemolyticus, and white spot syndrome virus (WSSV) were performed to evaluate pathogen resistance. While growth parameters did not differ significantly, prawns in biofloc systems exhibited higher survival and improved baseline immunity. The 150 mg/kg astaxanthin group showed significant enhancement of lysozyme activity, phagocytic index, and antioxidant enzyme activity (p < 0.001), whereas the 300 mg/kg group achieved the highest survival against WSSV (83.3 %) with reduced viral loads in hepatopancreas tissue. These findings demonstrate that dietary astaxanthin, particularly when combined with biofloc-derived microbial stimulation, potentiates both cellular and humoral components of innate immunity, thereby improving resilience to bacterial and viral infections. This integrative strategy highlights a sustainable, antibiotic-free approach to disease management in crustacean aquaculture.