Protective Effects of Ginger and Bacillus licheniformis on Mucosal and Humoral Immunity of Acanthopagrus latus Exposed to Cadmium

Cadmium (Cd) contamination poses a major threat to the health of farmed marine fish, promoting immunosuppression and bioaccumulation in tissues. In the present study, we determined the protective effects of dietary ginger (Zingiber officinale, 1%) and the probiotic Bacillus licheniformis (108 CFU/g) against Cd toxicity in yellowfin seabream (Acanthopagrus latus) by examining fish fed with these feeds individually and in combination. The trial consisted of a 42-day pre-feeding period followed by a 14-day co-exposure period to Cd, totaling 56 days of supplemented feeding. After the 42-day feeding period, fish were exposed to a sublethal Cd concentration (3.49 mg/L, 1/10 LC₅₀) for 14 days while continuing to receive the experimental diets. Haematological variables (Red Blood Cell, White Blood Cell counts, haemoglobin, haematocrit, and lymphocyte percentage), immune responses (lysozyme, complement, bactericidal, protease, esterase, and total immunoglobulin in plasma and skin mucus), and Cd accumulation in the gills were evaluated. Haematological parameters (p<0.05) and humoral and mucosal immune activities (lysozyme, complement, bactericidal, protease, and Ig in plasma and skin mucus) significantly increased during Cd stress in all supplemented diet groups (p<0.05) when compared to the Cd-exposed control. The accumulated Cd concentration in the gills of fish fed supplemented diets significantly decreased (p<0.05). Combined supplementation with ginger and B. licheniformis was associated with improved immune-related responses and reduced Cd accumulation in gills, suggesting their potential to mitigate Cd-related effects in yellowfin seabream.