Effect of dietary carbohydrate levels on growth performance, non-specific immune enzymes and acute response to low salinity and high temperature of juvenile sea cucumber Apostichopus japonicus
This study was performed to determine the optimum dietary carbohydrate (CHO) levels of sea cucumber, based on the parameters of growth, digestive enzymes, digestibility, non-specific immune enzymes and acute low-salinity (20 g/L) stress and high-temperature (30°C) stress tolerance. Diets with eight different CHO (dextrin) levels (32.9, 107.6, 192.5, 257.2, 316.8, 428.0, 482.4 and 572.8 g/kg) were fed to sea cucumber juveniles (0.49 ± 0.01 g) for 60 days. Significant higher amylase activity was observed in sea cucumbers fed diet with CHO ranging between 32.9 and 192.5 g/kg than that of other treatments ( p < .05). The sea cucumbers fed with 192.5 g/kg CHO showed significantly higher acid phosphatase activity than the treatments of 482.4 and 572.8 g/kg CHO ( p < .05), and significantly higher alkaline phosphatase activity than other treatments ( p < .05, except 257.2 g/kg). The treatments of 428.0–572.8 g/kg were found significantly lower values than other treatments in apparent digestibility coefficients for dry matter and crude protein ( p < .05). The sea cucumbers fed with 192.5, 257.2 and 316.8 g/kg CHO showed better tolerance to high-temperature (30°C) and low-salinity (20 g/L) stress than other treatments. In brief, the optimal dietary CHO level for the growth of juvenile sea cucumber is 177.96 g/kg. However, excessive CHO will inhibit amylase enzyme activity and decrease digestibility, resulting in low growth of sea cucumber.
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