Dietary cauliflower (Brassica oleracea var. botrytis) mitigates benzo[a]pyrene-induced oxidative stress, immune dysfunction, and tissue damage in Nile tilapia

Benzo[a]pyrene (BaP) is a ubiquitous polycyclic aromatic hydrocarbon that has been reported to induce immunotoxicity and oxidative stress in fish. In the current study, the potential protective efficacy of dietary cauliflower powder (CAF; Brassica oleracea var. botrytis) is investigated in Nile tilapia (Oreochromis niloticus) subjected to water-borne BaP exposure. Fish (initial body weight 35.45 ± 5.33 g; n = 280) were randomly assigned to seven groups (n = 40/group): control, acetone (12.25 µL/L), CAF0.5 (0.5%), CAF1 (1%), BaP (12.25 µg/L), CAF0.5 + BaP, and CAF1 + BaP, and maintained on their respective regimens for 30 days. Exposure to BaP induced 30% cumulative mortality, accompanied by distinct clinical-behavioral abnormalities, hepato-renal dysfunction, and depleted total protein fractions. Concurrently, stress biomarkers (glucose and cortisol) and lipid peroxidation (malondialdehyde) were markedly elevated. BaP exposure also suppressed antioxidant-immune responses, caused severe hematological alterations, disrupted splenic gene expression, and provoked pronounced histopathological lesions across multiple tissues (liver, brain, gills, and muscle). This damage correlated with high BaP bioaccumulation in muscle tissue and compromised resistance against Aeromonas hydrophila infection. Remarkably, dietary CAF intervention, particularly at the 1% inclusion level, significantly counteracted these toxic effects (P < 0.05). CAF supplementation reduced mortality, restored biochemical and immune profiles, lowered muscle BaP residues, and partially preserved normal tissue architecture. Furthermore, CAF-fed fish exhibited significantly enhanced post-challenge survival rates against A. hydrophila. Overall, these findings demonstrate that dietary CAF supplementation serves as an effective nutritional strategy to mitigate BaP-induced toxicity and support fish health in contaminated aquaculture environments.