Abstract
A 60-day research was conducted to evaluate the influence of dietary fish oil (FO) and selenium nanoparticles (SeNPs) on performance of Penaeus vannamei 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) FO(3)Se(0.4)SW (3% FO + 0.4 mg/kg SeNPs reared in SW), (2) FO(3)Se(0.8)SW (3% FO + 0.8 mg/kg SeNPs reared in SW), (3) FO(6)Se(0.4)SW (6% FO + 0.4 mg/kg SeNPs reared in SW), (4) FO(6)Se(0.8)SW (6% FO + 0.8 mg/kg SeNPs reared in SW), (5) FO(3)Se(0.4)HS (3% FO + 0.4 mg/kg SeNPs reared in HS), (6) FO(3)Se(0.8)HS (3% FO + 0.8 mg/kg SeNPs reared in HS), (7) FO(6)Se(0.4)HS (6% FO + 0.4 mg/kg SeNPs reared in HS), and (8) FO(6)Se(0.8)HS (6% FO + 0.8 mg/kg SeNPs reared in HS). Four hundred and eighty P. vannamei 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 FO(6)Se(0.4)SW and FO(6)Se(0.8)SW had higher weight gain (WG) compared to those in FO(3)Se(0.8)SW and FO(3)Se(0.4)HS (p < 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 FO(3)Se(0.4)SW, FO(6)Se(0.4)SW, FO(6)Se(0.8)SW, and FO(6)Se(0.4)HS 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 (lec), peneidine 3 (pen-3), prophenoloxidase (propo), and lysozyme (lyz) 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 P. vannamei tolerance to HS water.