Dietary selenium requirement and its toxicity in juvenile abalone Haliotis discus hannai Ino

A study was conducted to evaluate the effects of dietary selenium (Se) on survival, growth performances and immune responses of juvenile abalone Haliotis discus hannai. Moreover, the toxicity of high dose of dietary selenium was also analyzed. Six semi-purified diets containing graded levels of sodium selenite (0.15, 0.53, 0.88, 1.55, 2.63 and 9.16 mg Se/kg diet) were randomly fed to juvenile abalone (initial weight: 0.68 ± 0.00 g) in triplicate groups for 24 weeks in a flow-through system. Results showed that the weight gain ratio (WGR, %) of abalone fed 1.55 mg/kg of dietary selenium was significantly (P < 0.05) higher than that with 9.16 mg/kg of dietary selenium. However, there were no significant (P > 0.05) differences when compared to the other treatments. Selenium concentration in the soft body and the activity of glutathione peroxidase in serum were significantly (P < 0.05) increased with dietary selenium. Significant higher activities of phenoloxidase (PO) and lysozyme in serum were observed in the treatment with 0.88 mg Se/kg diet, compared with those in 9.16 mg Se/kg diet. However, the protein concentration in serum maintained relatively constant regardless of dietary treatments. The dietary selenium requirement of juvenile abalone was estimated to be 1.408 mg/kg, using second-order polynomial regression analysis. The toxicity of high level of dietary selenium (9.16 mg/kg) to juvenile abalone was characterized by depressed growth performances and decreased activities of PO and lysozyme in serum.

► Dietary selenium requirement of juvenile abalone was 1.408 mg/kg.
► High level of dietary selenium (9.16 mg/kg) was toxic to juvenile abalone.
► The toxicity was characterized by depressed growth performances.
► The toxicity also decreased the activities of phenoloxidase and lysozyme in serum.