Effects of dietary silymarin and chitosan nanoparticle-encapsulated silymarin on growth, liver function, and antioxidant responses in zebrafish

The present study aimed to evaluate the effects of dietary silymarin (SM), chitosan nanoparticles (CNPs), and silymarin-coated chitosan nanoparticles (SM-CNPs) on growth performance, liver function, antioxidant status, and the expression of antioxidant-related genes in zebrafish ( Danio rerio ). A total of 480 zebrafish (initial weight: 0.25 ± 0.005 g) were randomly assigned to four dietary treatments: a control diet without additives and diets supplemented with SM, CNPs, or SM-CNPs at 100 mg kg⁻ 1 feed for 8 weeks. Growth performance was not significantly affected by any dietary treatment ( P > 0.05). However, fish fed SM- or CNP-supplemented diets exhibited significantly lower serum alkaline phosphatase (ALP) and alanine aminotransferase (ALT) activities than the control group ( P < 0.05), indicating improved liver function. Moreover, dietary SM and SM-CNPs significantly reduced hepatic malondialdehyde (MDA) levels ( P < 0.05), while all supplemented diets significantly enhanced the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) compared with the control ( P < 0.05). Consistently, the expression of sod and gpx genes was significantly upregulated in fish receiving the supplemented diets ( P < 0.05). These findings demonstrate that dietary supplementation with SM, particularly when combined with chitosan nanoparticles, effectively enhances antioxidant defense and liver health without affecting growth performance, supporting its potential application as a functional feed additive for improving fish health in aquaculture.