Dietary Selenium-Enriched Yeast Boosts Antioxidant Defense, Flesh Quality and Selenium Accumulation in Adult Common Carp (Cyprinus carpio)

Selenium (Se) exerts essential biological functions via selenoprotein-mediated antioxidant defense and redox homeostasis. Selenium-enriched yeast (SEY) is a high-bioavailability organic Se source widely used in aquaculture. However, its effects on flesh quality in adult common carp (Cyprinus carpio) remain unclear. This study investigated the effects of graded dietary SEY on growth, muscle quality, Se deposition, antioxidant status, and associated metabolic responses in adult common carp. Results demonstrate that SEY supplementation (1.84 and 2.56 mg Se/kg) significantly improved growth performance without impairing physiological homeostasis. Mechanistically, SEY dose-dependently strengthened muscular antioxidant defense, with glutathione peroxidase activity increased by up to 7-fold, alongside elevated superoxide dismutase and catalase activities and reduced malondialdehyde content. This enhanced antioxidant capacity may maintain myofibrillar and membrane integrity, potentially contributing to the improvement of water-holding capacity and textural properties. SEY elevated umami amino acids and flavor nucleotides. Furthermore, in the 2.56 mg Se/kg supplemented group, SEY also increased muscle crude protein as well as organic Se deposition, with >99.99% of selenium present as selenocystine and selenomethionine. Untargeted metabolomics revealed that SEY reshaped the metabolome, enriching nucleotide metabolism and arginine biosynthesis pathways, which may partly account for the observed changes in umami-associated compounds. In conclusion, dietary SEY supplementation is an effective strategy for producing high-quality, Se-biofortified common carp.