Abstract
Improving the growth and immune responses are important to enhance the production efficiency of cultured juvenile sea cucumber Apostichopus japonicus. Here, 300 sea cucumbers (2.31 ± 0.01 g) were fed artificial diets with four concentrations of dietary chromium picolinate (Cr-Pic) supplementation (0, 0.3, 0.6 and 0.9 mg/kg) for 56 days. The growth performance, digestive enzyme activity (lipase, amylase and pepsin), expressions of growth-related genes (MAPK-7 and c-myc), and immune and antioxidant capacity were subsequently assessed. The present study found that final body weight, body weight gain and specific growth rate first increased and then declined with the increase of dietary Cr-Pic supplementation, while the highest values were observed in group 0.6 mg/kg. Consistently, significantly greater feed intake and significantly lower feed conversion ratio occurred in group 0.6 mg/kg than those in control group. Significantly better activities of lipase and amylase, and significantly higher expressions of genes MAPK-7 and c-myc were detected in group 0.6 mg/kg than those in control group. These results suggest that dietary Cr-Pic supplementation greatly improves the food utilization and expressions of growth-related genes, which consequently promotes the growth of sea cucumbers. Further, the activities of immune enzymes (alkaline phosphatase and lysozyme) and antioxidant enzymes (superoxide dismutase and total antioxidant capacity) in group 0.6 mg/kg were all significantly higher than those in control group. This indicates that dietary Cr-Pic supplementation significantly facilitates the immune and antioxidant capacity of sea cucumbers. In conclusion, we suggest dietary Cr-Pic supplementation with 0.6 mg/kg is the optimal level contributing to the growth and non-specific immune responses in the juvenile sea cucumber.
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