The Interactive Effects of Dietary Fish Oil and Selenium Nanoparticles Increased Growth, Antioxidant Capacity, and Immune‐Related Genes Transcription Level in <i>Penaeus vannamei</i> Reared in Hypersaline Water

A 60-day research was conducted to evaluate the influence of dietary fish oil (FO) and selenium nanoparticles (SeNPs) on performance of <i>Penaeus vannamei</i> juveniles (2.4 ± 0.0 g) reared in seawater (SW) or hypersaline (HS) water conditions. A 2 × 2 × 2 factorial research was designed with two FO levels, including 3% and 6%, two SeNPs dosages, including 0.4 and 0.8 mg/kg and two water salinity, including SW (35 g/L) and HS (50 g/L). Eight experimental groups were designed as follow: (1) FO₃Se^0.4SW (3% FO + 0.4 mg/kg SeNPs reared in SW), (2) FO₃Se^0.8SW (3% FO + 0.8 mg/kg SeNPs reared in SW), (3) FO₆Se^0.4SW (6% FO + 0.4 mg/kg SeNPs reared in SW), (4) FO₆Se^0.8SW (6% FO + 0.8 mg/kg SeNPs reared in SW), (5) FO₃Se^0.4HS (3% FO + 0.4 mg/kg SeNPs reared in HS), (6) FO₃Se^0.8HS (3% FO + 0.8 mg/kg SeNPs reared in HS), (7) FO₆Se^0.4HS (6% FO + 0.4 mg/kg SeNPs reared in HS), and (8) FO₆Se^0.8HS (6% FO + 0.8 mg/kg SeNPs reared in HS). Four hundred and eighty <i>P. vannamei</i> were randomly distributed into 24 250-L cylindrical fiberglass tanks. Each experimental group was replicated in three tanks (20 shrimp/tank). Shrimps were fed at 5% of their initial biomass three times daily. Water temperature and dissolved oxygen levels were maintained at 31.5 ± 1.2°C and 5.5 ± 1.0 mg/L, respectively. Shrimp in FO₆Se^0.4SW and FO₆Se^0.8SW had higher weight gain (WG) compared to those in FO₃Se^0.8SW and FO₃Se^0.4HS (<i>p</i> < 0.05). Rearing shrimp in HS water increased whole-body protein and ash contents but reduced moisture level. The amount of docosahexaenoic acid (DHA) in FO₃Se^0.4SW, FO₆Se^0.4SW, FO₆Se^0.8SW, and FO₆Se^0.4HS was relatively higher than the other treatments. The antioxidant activities, including glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) level decreased and malondialdehyde (MDA) content in hepatopancreas increased in shrimp reared in HS water. Finally, the transcription levels of insulin-like growth hormones and immune-related genes, including lectin (<i>lec</i>), peneidine 3 (<i>pen-3</i>), prophenoloxidase (<i>propo</i>), and lysozyme (<i>lyz</i>) increased by increasing dietary FO level of 6%. Additionally, these levels were modulated by the interaction of water salinity and dietary SeNPs and FO levels. Based on the findings of the current study, increasing the dietary FO level to 6% and incorporating a moderate level of SeNPs (0.4 mg/kg) were found to enhance <i>P. vannamei</i> tolerance to HS water.