Lead Acetate Exposure Induces Growth Retardation, Immune Suppression, Oxidative/Antioxidant Imbalance, and Histological Alterations in Oreochromis niloticus: A Mitigation Trial via Chlorella vulgaris

Lead pollution is a common problem in aquatic environments and poses serious health hazards. Fish are extremely susceptible to Pb accumulation, which hinders their growth and general health. This study examined the effects of water-borne Pb acetate on the biological indices, tissue architecture, and growth of Oreochromis niloticus. The ability of dietary Chlorella vulgaris (CV) microalgae to protect against Pb exposure was also investigated. A total of 270 healthy O. niloticus (42.4±0.21 g) were divided into six groups (45 fish/group). The CTR (control) and Pb groups were fed a basal diet and exposed to 0, 5, or 10 mg/L Pb. The CV groups were fed a diet supplemented with 10% CV and exposed to 0, 5, or 10 mg/L Pb for 56 days. The results revealed that Pb exposure caused growth retardation in a dose-dependent manner, with significant decreases (P˂0.05) in immunological and antioxidant indices. Pb exposure was associated with a significant increase (P˂0.05) in the serum levels of lipid peroxidation and hepatorenal biomarkers. Exposure to Pb caused an increase in IL-12 gene expression and a significant, dose-dependent tissue-damaging effect. Compared with Pb-exposed non-fed fish, the growth, immunity, antioxidant status, hepatorenal functions, and expression of IL-12 of the Pb-exposed fish were considerably modulated when fed CV diets. The tissue architecture, chemical body composition, and Pb residue levels in the muscles of Pb-exposed fish were all enhanced by CV. Crucially, CV could be administered as a feed supplement to improve the health and productivity of Pb-exposed O. niloticus.