Effects of dietary fermented attachments of suspension cage as a replacement for sea mud on growth and intestinal health of sea cucumber Apostichopus japonicus

In the suspension cage culture process, regular cleaning to remove epiphytic organisms from the cage is essential to prevent economic losses due to the sinking of the cage. However, after cleaning, many of attachments from the suspension cage accumulate in the tidal flats, causing environmental pollution and resource wastage. Moreover, because sea cucumbers (Apostichopus japonicus) are sedimentary food organisms, sea mud is typically added to their feed to varying degrees. However, long-term excavation of sea mud can destroy the marine environment. Therefore, developing an alternative new raw feed material to replace sea mud in sea cucumber feed is necessary to promote sustainable development of the A. japonicus aquaculture industry. The aim of this study was to explore the feasibility of using fermented attachments of suspension cage (FASC) as a raw feed material for A. japonicus. Different FASC concentrations (0, 25, 50, 75, and 100 %) were used in A. japonicus feed for 60 d. Replacing Sea mud with 100 % FASC significantly improved sea cucumber growth, reduced the feed coefficient, significantly increased the activity of intestinal digestive enzymes, improved intestinal structure, and enriched intestinal microbiome diversity. Furthermore, expressions of growth genes mapk-7 and fgfr-1 significantly increased in the 100 % FASC treatment compared with that in the control, and that of negative growth regulator gene gdf-8 was inhibited. The results suggested the potential of FASC as a new raw feed material for A. japonicus.