Supplementation of juvenile Siberian sturgeon (Acipenser baerii) diet with different levels of selenium: Growth performance, digestive enzyme activities, and intestinal histomorphology

This study aimed to investigate the impact of dietary Selenium (Se) on the growth performance, body composition, digestive enzymes, and intestinal histomorphology of Siberian sturgeon, Acipenser baerii. Fish (10.0 +/- 0.5 g) were randomly assigned to fifteen 1000-L tanks (30 fish per replicate) in a flow-through system and fed three times a day (08.00, 13.00, 18.00) with isonitrogenous (54.21 % crude protein) and isolipidic (15.63 % crude lipid) diets supplemented with selenomethionine at levels of 0, 0.2, 0.4, 0.8, and 1.6 mg kg(-1) providing the analyzed Se of 0.10, 0.29, 0.49, 0.88, and 1.70 mg kg(-1), respectively. Each three tanks were allocated to each treatment. After the eight-week feeding trial, weight gain ratio, specific growth rate, and survival rate of fish significantly increased with increasing dietary Se supplementation (p<0.05) and reached to the highest values of 156.00 +/- 0.68 %, 1.68 +/- 0.07 % d(-1), and 98.33 +/- 1.66 %, respectively, while the feed conversion ratio declined to the lowest value of 1.79 +/- 0.10. Protein and lipid content increased with Se levels to the highest values of 20.15 +/- 0.11 % and 8.23 +/- 0.05(%), respectively (p<0.05). Activity of all digestive enzymes including trypsin, chymotrypsin, alpha-amylase, lipase, and alkaline phosphatase significantly enhanced with increasing dietary Se levels (p<0.05). Increasing trends in villus height, villus width, muscle thickness, and crypt depth were found by increasing dietary Se supplementation with the highest values of 502.33 +/- 31.25, 134.39 +/- 13.12, 194.18 +/- 11.37, and 67.29 +/- 0.12 <mu>m, respectively, in fish fed diet supplemented with 1.70 mg kg(-1) Se (p<0.05). Findings of the present study illustrated the beneficial effects of dietary Se on performance, digestive enzymes, and intestinal histomorphology of Siberian sturgeon. According to the polynomial regression analysis, the optimum dietary requirement of Siberian sturgeon was in the range of 1.47-1.69 g kg(-1).