Effects of different levels of sweet potato in feeds on body composition and digestive enzymes activities of Apostichopus japonicas Selenka

Abstract

The aim of this study was to test the effects of including sweet potato tuber and stem powder in feed on the body composition and digestive enzyme activities of the sea cucumber Apostichopus japonicas Selenka. Different proportions of sweet potato tuber and stem powders (from 10% to 50%) were added into compound feeds, which were supplied to A. japonicas during a 60-day experiment. The results showed that the two sweet potato ingredients had different effects on the nutrient contents of the sea cucumber body wall. The group supplied with feed containing 20% sweet potato tuber powder (T2) had the highest level of crude protein in body walls ( P 0.05). In all the groups fed with powdered sweet potato tubers (T groups), the proportions of glutamic acid and lysine in body walls were higher than those in the control, whereas the proportion of methionine decreased slightly. Different proportions of sweet potato ingredients in compound feeds also affected digestive enzyme activities in the sea cucumbers. The activities of protease and lipase first increased and then gradually decreased with increasing proportions of sweet potato materials in the feed. The highest protease activity was in the T2 and the group and the highest lipase activity was in the 10% sweet potato stem (S1) group. These results show that feed components can stimulate digestive enzyme activities in sea cucumber, and that the proportions of tubers and stems of sweet potato in feed can be adjusted to improve the digestion and growth of A. japonicas in marine farms.