Dietary coated sodium selenite enhances muscle growth associated with mitochondrial function in sub-adult grass carp (Ctenopharyngodon idellus)

Selenium (Se) is a vital trace element necessary for fish growth and health. This research aimed to elucidate the beneficial impacts of coated sodium selenite (CSS) on sub-adult grass carp muscle and compared effects of CSS and sodium selenite (SS). A total of 450 healthy fish (average weight: 687.33 ± 1.15 g) were randomly divided into six groups, each fed diets containing CSS levels (0.028, 0.25, 0.50, 0.75, and 1.00 mg/kg Se) and SS (0.50 mg/kg Se) for eight weeks. Results indicated that optimal CSS enhanced body length and increased Se concentrations in muscle and hepatopancreas ( P < 0.05). The accumulated Se further up-regulated the expressions of selenoproteins (such as gpx1 and selp ), which collectively improved antioxidant capacity [such as glutathione peroxidase (GPX) activity and L-glutathione (GSH) content] and mitochondrial quality (such as fusion, biogenesis and respiratory chain) ( P < 0.05). These changes promoted muscle fiber development via enhanced protein ( pi3k , akt , and s6k1 ) and extracellular matrix synthesis ( col1α1 , smad2 , smad4 , tgf-β1 , and phd ) ( P < 0.05). Interestingly, at the 0.50 mg/kg Se supplementation, CSS and SS showed similar growth and muscle development, but different signaling pathway responses, indicating potential extra benefits of CSS. Overall, dietary Se could enhance muscle growth in sub-adult grass carp by dual mechanisms: enhancing antioxidant defenses and improving mitochondrial quality.