Effects of Short-Term Dietary Sodium Selenite Supplementation on Antioxidant Status, Heavy Metal Deposition, Flesh Quality and Flavor-Related Compounds of Common Carp (Cyprinus carpio), and a Potential Mechanism

Sodium selenite is a cost-effective selenium source widely used in aquafeed, yet its effects on the flesh quality of adult common carp (Cyprinus carpio) remain poorly understood. Using a short-term feeding trial simulating pre-harvest selenium biofortification, this study investigated dietary sodium selenite effects on growth, antioxidant status, selenium deposition, heavy metal accumulation, nutritional composition, and flavor-related compounds in adult common carp. Dietary selenium supplementation improved weight gain and specific growth rates, with optimal doses ranging from 1.797 to 1.804 mg Se kg−1. Elevated hepatic and muscular glutathione peroxidase (GSH-Px) and catalase (CAT) activities, coupled with decreased malondialdehyde (MDA) concentrations, were closely associated with increased selenium deposition in muscle. Selenium deposition was also correlated with decreased accumulation of heavy metals (Hg and Cd), which may be attributable to the formation of inert complexes. The improved antioxidant status was further linked with better muscle texture and water-holding capacity. Moreover, dietary sodium selenite increased muscle crude protein content and the abundance of umami-active free amino acids. The proportional content of total eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) increased from 3.55% to 5.14%, accompanied by alterations in flavor-related volatile compounds. Untargeted metabolomic analysis further revealed that dietary selenium supplementation substantially modulates lipid metabolism, as well as PPAR and FoxO signaling pathways. Collectively, these findings offer experimental insights supporting the development of selenium-enriched common carp production under short-term pre-harvest fortification strategies.