Unveiling the role of Alcea rosea in modulating growth, immunity, antioxidant defenses, and gene expression in zebrafish (Danio rerio).

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Novel and natural alternative feed ingredients are essential for sustainable aquaculture sector. For a period of 60 days, this study examined the effects of incorporating Hollyhock (Alcea rosea) powder into the diet on gene expressions, growth parameters, serum biochemical and innate immune parameters, as well as antioxidant capacity in zebrafish (Danio rerio). Fish, with an initial weight of (302.66 ± 3.75) mg, were seperated into four groups. Each group was fed a diet containing varying percentages of Hollyhock: 0% (AR0), 0.5% (AR05), 1% (AR1), and 2% (AR2). Growth performance was significantly enhanced in the AR2 group, with no significant differences observed in the other groups. The supplementation of Hollyhock led to significant alterations in the serum biochemical parameters, specifically alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP), resulting in notably lower levels compared to the AR0 group. The Hollyhock-supplemented diet led to a significant increase in both total protein and total immunoglobulin levels, as compared to the AR0 group. There were no changes observed in CAT activity related to antioxidant defense, while exclusive to the AR05 group, a substantial elevation was observed in SOD activity compared to the AR0 group. The results shown that the expression levels of growth-related genes, such as GH and IGF-1, showed an increase in all diets supplemented with Hollyhock. Growth exhibited a statistically significant difference in group AR2, while no significant difference was observed in the other groups. The Heat Shock Protein 70 gene (HSP70) was downregulated specifically in the AR1 group. Immune-related genes, including LYZ, IL-1β, and TNF, were significantly upregulated with Hollyhock supplementation. Both LYZ and TNF showed the highest expression in the AR1 and AR2 groups, while IL-1β peaked in the AR1 group. In terms of antioxidant-related genes, Antioxidant-related genes, SOD and CAT, were significantly upregulated in Hollyhock-treated groups. SOD expression peaked in the AR1 group, and CAT was most upregulated in the AR1 and AR2 groups. Overall, these results suggest that supplementation with 1-2% Hollyhock in the diet of zebrafish positively influenced growth, immunity, antioxidant defense, and serum biochemical parameters, making it a promising feed additive for enhancing aquaculture productivity and fish health.