Dietary selenium nanoparticles positively modulate the growth and immunity of seabream (Sparus aurata) fingerlings exposed to low salinity stress and Vibrio parahaemolyticus challenge

This study aimed to investigate the effects of selenium nanoparticle (Nano-Se) supplementation on the growth performance, physiological parameters, antioxidant system, and immune response of seabream (Sparus aurata) under normal conditions, as well as after low salinity stress and challenge with Vibrio parahaemolyticus. The fish were divided into five experimental groups that received experimental diets supplemented with different levels of Nano-Se (0, 0.125, 0.25, 0.5, and 0.75 mg/kg Nano-Se) for 14 weeks. The results revealed that Nano-Se supplementation had a positive impact on growth performance, including final weight, weight gain, daily weight gain, specific growth rate, and feed conversion ratio. Nano-Se significantly increased the expression of insulin-like growth factors 1 and 2. The findings suggest that Nano-Se promotes growth in seabream under both normal and stressful conditions. Low salinity stress and Vibrio parahaemolyticus challenge were found to increase the levels of serum cortisol and the heterophil and lymphocyte (H/L) ratio while decreasing the population of lymphocytes, white blood cells, and immunoglobulin M. However, Nano-Se supplementation mitigated these effects. Nano-Se exhibited a protective effect by restoring the H/L ratio to normal levels and enhancing the immune response. Our expression analyses indicated a significant interaction between Nano-Se and stress. NanoSe reduced the upregulated levels of heat shock protein 70 and interleukin 1 & beta; caused by low salinity and bacterial challenge, bringing them closer to normal values, compared to the groups without Nano-Se supplementation. Nano-Se slightly increased the mRNA levels of interleukin 1 & beta; under healthy conditions, particularly at concentrations of 0.5 and 0.75 mg/kg. Additionally, Nano-Se improved the serum biochemical profiles and carcass composition of seabream. Notably, the concentrations of 0.5 and 0.75 mg/kg increased the survivability of seabream exposed to low salinity stress and V. parahaemolyticus challenge. These findings suggest that Nano-Se can be effectively utilized to enhance the health and performance of seabream in aquafarms.