Effects of dietary rhubarb, Bacillus cereus, yeast polysaccharide, and florfenicol supplementation on growth, intestinal morphology, and immune responses of sea cucumber (Apostichopus japonicus) Gang Yang 1,2 • Xiangli Tian 1 • Shuanglin Dong 1 • Mo Peng 3 • Dongdong Wang 1 • Kai Zhang 1 Received: 31 May 2015 / Accepted: 31 October 2015 Ó Springer International Publishing Switzerland 2015 Abstract A 60-day feeding trial was conducted to investigate the effects of dietary Chinese herbal medicine (rhubarb, Rheum officinale Bail), probiotic (Bacillus cereus BC- 01), prebiotic (yeast polysaccharide), and antibiotic (florfenicol) supplementation on the growth, intestinal morphology, and immune responses of juvenile sea cucumbers (Apos- tichopus japonicus Selenka; initial weight, 4.67 ± 0.06 g). The control treatment was fed only the basal diet (CT treatment), whereas four other treatments were fed the basal diet supplemented with rhubarb (RH treatment), B. cereus BC-01 (BC treatment), yeast polysaccharide (PO treatment), or florfenicol (FL treatment). Groups of ten sea cucumbers were housed in separate tanks, and each diet was fed to five randomly selected groups. The specific growth rates of the individuals in the RH and BC treatments were significantly higher than those in the CT, PO, and FL treatments. The apparent digestibility coefficient of crude protein in the RH and BC treatments was significantly higher than that of crude protein in the CT and PO treatments. The alkaline phosphatase activity of the coelomo- cytes in the RH and BC treatments was significantly higher than that in the CT and FL treatments. Coelomocytes in the PO treatment had the highest acid phosphatase activity. Higher than average lysozyme activity was observed in the PO and FL treatments. Fold and enterocyte heights in the mid-intestinal tract of sea cucumbers in the CT and RH treatments were lower than those in the BC, PO, and FL treatments. Microvillus height was greatest in the RH treatment and lowest in the FL treatment. Scanning electron microscopy revealed remarkable atrophy of microvilli and apoptosis of intestinal epithelial cells in the FL treatment. These results suggest that dietary rhubarb, B. cereus, and yeast polysaccharide & Xiangli Tian xianglitian@ouc.edu.cn 1 The Key Laboratory of Mariculture, Ministry of Education, Fisheries College, Ocean University of China, Qingdao 266003, China 2 Department of Bio-Science, Institute of Life Science, Nanchang University, Nanchang 330031, China 3 School of Animal Science and Technology, Jiangxi Agricultural University, Nanchang 330045, China 123 Aquacult Int DOI 10.1007/s10499-015-9957-9