Abstract:In this study, the diets for sea cucumbers (Apostichopus japonicus Selenka) were formulated with Enteromorpha prolifera, Ulva lactuca, soybean meal, glucose, scallop side, shell powder, vitamins premix and mineral premix, and processed in four ways using Brewer’s yeast and alkaline protease. The final products were 5 groups of experimental diets including the control group, the fermented group, the hydrolyzed group, the composite group and the fresh-group. Each diet was randomly given to 3 replicates of 30 sea cucumbers of which the average body weight was (1.92±0.02) g. The results were described as follows. E. prolifera-diets had significant different effects on the survival rate (SR), the weight gain rate (WGR), the specific growth rate (SGR) and the feed coefficient (FC) (P<0.05). The SR in the composite group and the fresh group was higher than that in the hydrolyzed group (P<0.05), but was not significantly different from other groups (P>0.05). The WGR in the fresh group was higher than that in other groups (P<0.05). The FC in the fresh group was lower than in all other groups except for the composite group. Over the feeding time, the intestinal amylase activity (AMS) showed an increasing-decreasing-stabilized pattern in the control group, the fermented group, the composite group and the fresh group; however, AMS had been constantly declining in the hydrolyzed group. The intestinal cellulase activity in the hydrolyzed group tended to decrease over time, and in other groups, it was higher than the initial values and had been fluctuating. Except for the hydrolyzed group, the trypsin activity in all other groups showed no significant change. E. prolifera-diets also affected the activities of acid phosphatase (ACP), alkaline phosphatase (AKP) and superoxide dismutase (SOD) in the coelomic fluid to different extents (P<0.05). ACP in the fresh group was the highest and was significantly higher than all other groups (P<0.05) except for the composite group (P>0.05). SOD in the composite group was the highest and was significantly higher than the hydrolyzed group and the fermented group. These results suggested that juvenile sea cucumbers could benefit from the diets of the composite group and the fresh group in terms of the growth performance, the intestinal digestion and immunity. Our study also provided information on solving the shortage in raw dietary materials for sea cucumbers and making good use of E.prolifera.
