Mitigation Exposed to Cadmium Stress in Thinlip Grey Mullet (Liza ramada) By Dietary Fucoidan Derived from Sargassum muticum: Examining the Growth Performance, Immune Response, and Histopathological Alterations.

The current study aimed to investigate the potential effect of dietary fucoidan extract (Fuc) from Sargassum muticum in aiding the reduction of harmful effects of cadmium (Cd) in water on the growth, blood markers, intestinal health, antioxidants, immune marker responses, and histopathological changes in grey mullet (Liza ramada). Fish (n = 240) with similar initial weight (7.33 ± 0.1 g) were allocated to the control, fish reared without Cd exposure, and the Fuc; cadmium fish group was exposed to (1 mg Cd L) without Fuc. The fish were fed Fuc (1.0%) without the Cd group, and the fish were exposed to (1 mg Cd L) and fed the Fuc (1.0%) group for 60 days. Control, Cd, Fuc, and Cd/Fuc were the names of the groups. The data illuminated that growth performance, survival rate, blood indices, and intestinal health were markedly improved (P ≤ 0.001) in the Fuc group, followed by Cd/Fuc and the control groups. Conversely, these indices of the Cd group displayed a significantly negative impact (P ≤ 0.001). Concurrently, antioxidant (GPx, SOD, and CAT activities) and immune, lysozyme, and phagocytic activities markedly increased (P ≤ 0.001) in the Fuc group, followed by Cd/ Fuc, control groups, and the lowest values were recorded in the Cd group. Nonetheless, the Fuc group had lower MDA levels, whereas the Cd group had higher levels. Notably, the Fuc group revealed the upregulated expression of the GPx and IL-10 genes, followed by Cd/Fuc and the control groups, and downregulated the Cd groups. Furthermore, the genes HSP70, TNF-α, and IL-1β expression markedly downregulated (P ≤ 0.001) in Fuc, followed by Cd/ Fuc and control groups. Conversely, the expression of these genes upregulated in the Cd group (P ≤ 0.001). The histological analysis displayed that the Cd group had inflammatory and abnormal tissue (gills, intestines, and liver) characteristics, whereas the fish-fed Fuc displayed intact tissue. To enhance overall welfare and protect grey mullets from the toxicity of waterborne cadmium, this study suggests adding Fuc (1.0%) to mullet diets.