The impact of selenium sources and levels in the diets of Penaeus vannamei

This study investigated the effect of three selenium sources—sodium selenite (SS), selenium yeast (SeYeast), and hydroxy-selenomethionine (OH-SeMet) — at two dietary inclusion levels (0.3 and 0.6 mg/kg) on the antioxidant status, tissue integrity, stress resilience, growth performance, and flesh quality of Penaeus vannamei reared under low-salinity conditions. A 127-day feeding trial was conducted using a completely randomized design with six treatments applied throughout the nursery and grow-out phases. Overall, organic selenium sources (OH-SeMet and SeYeast) outperformed inorganic selenium (SS) in enhancing antioxidant capacity, selenium deposition, and hepatopancreatic integrity, with OH-SeMet providing the most consistent benefits. Selenium sources amplified antioxidant defenses particularly OH-SeMet, as evidenced by elevated reduced glutathione (GSH), glutathione peroxidase (GSH-Px) activity, and total antioxidant capacity (T-AOC). Shrimp fed OH-SeMet exhibited the best growth rates and biomass yield with the 0.6 mg/kg level supporting the highest growth followed by SeYeast, while SS consistently showed the poorest outcomes across all parameters. However, under nitrite-induced hypoxia, survival was significantly higher at the 0.3 mg/kg level, indicating stronger resilience to acute environmental stress. Improvements in flesh quality, including water-holding capacity, oxidative stability, and fillet firmness, were dose- and source-dependent, with OH-SeMet achieving the best results even after 60 days of frozen storage. These findings demonstrate a clear hierarchy among selenium sources—OH-SeMet > SeYeast > SS—and highlight the need to match inclusion level with production goals: 0.6 mg/kg OH-SeMet for maximizing growth under optimal conditions, and 0.3 mg/kg for enhancing stress resistance and tissue integrity in more variable environments.