Effect of dietary selenium on growth performance, survival rate and biochemical-blood profile of farmed juvenile beluga (Huso huso)

Beluga sturgeon (Huso huso), the largest freshwater fish, has attracted the attention of sturgeon culturists worldwide. The profitability of aquaculture beluga production mainly depends on physiologically suitable formulated diets. The objective of this research is to determine the optimal level of dietary selenium (Se) for beluga using the following parameters:  growth performance traits (WG, SGR, PER, and FER), body proximate composition, and serum biochemical and immunological indices (glucose, total protein, Ig M, lysozyme, ALT and AST). To this aim beluga (n=315; with initial weight of 15.66±0.77 g) were fed with diets supplimented with sodium selenite (0.18, 5.43, 12.6, 24.3, 37.2, 71.4, and 144 mg kg^-1) for 10 weeks. Unexpectedly, all of the parameters exhibited considerable responses to the applied levels of Se. Growth performance indices displayed the highest values for the animals treated with diets containing 12.6 and 24.3 mg kg^-1Se, yet the lowest ones with71.4 and 144 mg kg^-1 (i.e., U-form response). Similar response was seen for crude lipid and protein content as well as for the activity of ALT and AST, whereas IgM and lysozyme did an anticline manner (i.e., the highest values in the midle Se levels). Moisture and ash contents and also serum total protein exhibited a Se-dose dependent increase. Based on the broken line regression model, optimal dietary Se requirement for juvenile beluga is about 18.2 mg kg^-1. Taken together this study extends our knowledge on one of the most essential trace elements and its optimal level for incorporating into beluga diet. It  could also be a basic one in the sturgeon aquaculture industery.