Dietary sodium silicate improves growth performance, intestinal health, and cadmium-stress responses in juvenile common carp (Cyprinus carpio)

Cadmium (Cd) stress impairs growth, intestinal health, and immune function in fish. Supplementation with trace elements in nutritional supply to alleviate cadmium stress constitutes a mainstream approach in existing studies on plants and terrestrial animals, with silicon being a particularly prominent example. This study utilized sodium silicate as the silicon source in common carp feed to investigate the potential mechanisms and feasibility of supplementing this silicon source to enhance fish growth, intestinal health, and the ability to respond to cadmium stress. Five experimental diets containing graded levels of sodium silicate (0%, 0.25%, 0.5%, 1%, and 2%) were fed to triplicate groups of 30 fish each for 8 weeks. Results revealed that the 0.5% sodium silicate group exhibited significantly higher weight gain rate, specific growth rate, and protein efficiency ratio, as well as lower feed conversion ratio and feeding rate. The 0.5% group also showed maximal intestinal antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase, total antioxidant capacity) and upregulation of nrf2 , Cu/Mn-SOD , and Catalase ( cat ) gene expression, along with reduced malondialdehyde content. Enhanced expression of tight junction factors ( occludin , zo-1 , claudin 7 , claudin 11 ) and intact intestinal villus structure were observed. Based on the above findings, the 0%, 0.5%, and 2% groups were selected for the Cd stress. 0.5% group showed trends toward earlier transcriptional changes in certain immune-related genes ( zo-1 , mlck , claudin 3 , il-1β at 12 h) compared to the control group. These findings suggest that 0.5% dietary sodium silicate supplementation may serve as a potential candidate for improving growth performance, intestinal health and faster immune response on Cd stress in juvenile common carp under the experimental conditions of this study. These findings are preliminary and require validation through long-term trials and across different culture conditions before any practical recommendations can be made. Future studies should further elucidate the mechanism of action of sodium silicate through tissue Cd and Si accumulation measurements, chronic exposure experiments, and sodium control diets.