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摘要
An experiment was conducted to investigate the effects of diets containing Ulva prolifera from different sites on the growth, digestibility, digestive enzymes, and non-specific immunity enzymes of juvenile sea cucumber Apostichopus japonicas. The diets were composed of a dry powder of U. prolifera from Qingdao (QD) and Ningbo (NB), and each mixed with sea mud at a certain mass ratio, The QD group and NB group were compared with the sea cucumber feeding on a natural diet (ND) of Sargassum sp. Results show that the crude protein contents of QD group and ND group were 14.31%±0.10% and 15.43%±1.41%, significantly higher than that of NB group (11.17%±0.63%). Crude fats and ash contents had no significant difference among the three groups. The weight gain rates of DQ, NB, and ND groups were 22.65%±5.68%, 3.03%±1.17% and 20.47%±2.01%, and the specific growth rates (1.44±0.33)%/d, (0.21±0.08)%/d, and (1.33±0.12)%/d, respectively. The weight gain rates and specific growth rates of QD and ND were significantly higher than NB. The survival rates showed no significant difference among the three groups. Amylase, pepsase, cellulose, and trypsin activities were also similar among the three groups. Alkaline phosphatase activity of ND group was (17.57±4.56) King’s unit/100mL, significantly higher than QD [(5.56±1.32) King’s unit/100mL] and NB [(2.83±0.75) King’s unit/100mL] groups. Superoxide dismutase and acid phosphatase activities of sea cucumbers were similar among the three groups. Therefore, making use of U. prolifera in its bloom as a sea cucumber bait resource could not only mitigate the environmental hazard of the green tide but also increase ecological and market values. However, the nutrient levels of U. prolifera depends on complex factors. The variety, collection time, and site position of U. prolifera should be considered. Some pretreatments are suggested to maximize the bait value of U. prolifera.
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