Dietary selenium requirement of coho salmon (Oncorhynchus kisutch W.) alevins

A 12-week feeding trial was conducted to determine the optimal dietary selenium requirement for coho salmon (Oncorhynchus kisutch W.) alevins. Six experimental diets (contained about 42.2% crude protein and 10.5% crude lipid) were formulated to contain selenium level of 0.07, 0.15, 0.24, 0.41, 0.75, and 1.38 mg/kg, respectively. Each diet was fed to triplicate groups of fish with initial mean body weight of 0.38 +/- 0.01 g, which were randomly assigned to 18 plastic tanks (80 x 60 x 60 cm, length x width x height, water volume 240 L), and each tank was stocked initially with 50 fish. Fish were fed four times daily and used the method of overfeeding (15-20% body weight) to fish. The sampling procedure was implemented after 24 h of fasting. Results showed that specific growth rate (SGR) in 0.24, 0.41, and 0.75 mg Se/kg groups were significantly higher than those in 0.07 and 1.38 mg Se/kg groups (P < .05). There were no significant differences in hepatosomatic index (HIS), intestinal somatic index (ISI), condition factor (CF), and whole-body composition among dietary groups (P > .05). Hepatic malondialdehyde (MDA) content significantly declined with increasing dietary up to 0.41 mg Se/kg and increased as selenium further increased. The hepatic superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) significantly increased with increasing dietary selenium up to 0.41 mg/kg and decreased significantly as selenium further increased (P < .05). Fish fed diet with 0.75 mg Se/kg had the highest glutathione reductase (GR), which did not differ significantly with 0.41 and 1.38 mg Se/kg groups (P > .05) but significantly higher than those in 0.07, 0.15, and 0.24 mg Se/kg groups (P < .05). Broken-line regression analyses based on SGR, hepatic, and whole-body selenium contents indicated that the optimum dietary selenium requirements were in the range of 0.39-0.43 mg/kg for coho salmon alevins.

Automated summary

In a 12-week feeding trial, the impact of dietary selenium levels on coho salmon alevins showed varying growth and antioxidant enzyme activities. The optimal dietary selenium requirement for coho salmon alevins was determined to be in the range of 0.39-0.43 mg/kg.