Abstract:In order to evaluate the application of Sargassum thunbergii, Sargassum horneri, Saccharina japonica, degummed kelp, Ulva lactuca L., and their mixture in juvenile sea cucumbers [(10.02±0.03) g], an 8-week-long experiment was conducted in a circulating water system. Growth performance, body composition, intestinal digestive enzyme activities, and nonspecific immune performance were analyzed. Results showed that the weight gain rate (WGR) and specific growth rate (SGR) of sea cucumbers fed S. thunbergii and the seaweed mixture were significantly higher than those of other groups (P<0.01), and were the lowest in sea cucumbers fed degummed kelp. Sea cucumbers fed degummed kelp had significantly lower ratio of intestine weight to body weight (IBR) and ratio of viserosomatic weight to body weight (VBR) than those of the other groups (P<0.05). Different seaweed did not significantly affect survival rate (P>0.05). Body wall moisture, crude ash, crude protein, and the crude fat of sea cucumbers were not significantly affected by the seaweeds (P>0.05). The intestinal trypsin activities in sea cucumbers fed S. thunbergii, and the seaweed mixture were significantly higher than those in the kelp, degummed kelp, and Ulva groups, and were the lowest for degummed kelp (P<0.01). The different seaweeds had no significant effect on alpha amylase and lipase activity (P>0.05), but significant effects were observed in the hydrochloric acid-insoluble ash of fecal matter (P<0.01). Intestinal total-superoxide dismutase (T-SOD), acid phosphatase (ACP), and alkaline phosphatase (AKP) activities in the sea cucumbers fed S. thunbergii and seaweed mixture were significantly higher than those in the other groups (P<0.01). Intestinal malondialdehyde (MDA) content in sea cucumbers fed degummed kelp was significantly higher than that in the other groups (P<0.01). In conclusion, a comprehensive consideration of growth performance and nonspecific immune performance indicated that the four seaweeds individually cannot achieve the feeding effect of replacing dietary S. thunbergii; however, using mixed seaweeds can achieve an effect similar to S. thunbergii under these experimental conditions.
