Synergistic effects of nutritional supplementation of selenium and magnesium nanoparticles on growth and gastric enzymes of Asian sea bass (Lates calcarifer)

The aim of this study was to investigate the effect of selenium, magnesium nanoparticles and their composition on growth and digestive enzymes of Asian seabass with a mean weight of 32.78±1.16 g for 42 days. After adaptation to the experimental conditions, 96 fish were randomly distributed in 12 fiberglass cylinder 300-liter tanks in equal numbers. Four treatments including control treatment, 4mg / kg nanoselenium, 500mg / kg nanomagnasium and combination of 4mg/ kg nanoselenium with 500mg / kg nanomagnasium were investigated. The fish were fed daily in satiation and up to 3% of body weight in two time a day. Samples needed to measure growth indices and digestive enzymes were collected at the end of the period. The results showed that in the fish fed the combined treatment, the highest body weight gain was 131.33±26.58 and the specific growth rate was 2.08±0.28 and there was a significant difference between the control treatment (65.01±21.26 and 1.23±0.32, respectively) (P <0.05). The results of this study showed that digestive enzymes of alkaline phosphatase, lipase, trypsin and chymotrypsin were significantly different between experimental treatments (P <0.05), so that the highest activity of alkaline phosphatase in nanoselenium treatment (611.06±82.00U/mg protein),  the highest amount of lipase (0.86±0.03 U/mg protein), trypsin (0.054 ± 0.001 U/mg protein), and chymotrypsin (0.214±0.004U/mg protein) was seen in nanomagnesium treatment (P <0.05), whereas the amylase enzyme showed no significant difference between the experimental treatments (P> 0.05). The results of this study showed that the addition of selenium and magnesium nanoparticles to the diet of Asian Sea bass had positive effects on growth performance and digestive enzymes and suggested that magnesium nanoparticle supplementation (500 mg/kg) could be used alone or in combination with selenium nanoparticles (4 mg/kg nano-selenium and 500 mg / kg nano-magnesium) in the diet of Asian Sea bass.