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 with an initial average body weight of 687.33 ± 1.15 g were randomly assigned to six groups. Fish in these groups were fed experimental diets supplemented with graded levels of CSS (0.028, 0.25, 0.50, 0.75, and 1.00 mg/kg Se) and one diet containing SS at 0.50 mg/kg Se, respectively, for an 8-week feeding trial. Results indicated that optimal CSS increased body length and 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 alterations improved muscle fiber development by upregulating the expression of genes related to protein synthesis (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 responses in signaling pathways, implying that CSS may confer additional physiological benefits. Overall, dietary Se could enhance muscle growth in sub-adult grass carp by dual mechanisms: enhancing antioxidant defenses and improving mitochondrial quality.