Effects of dietary levan on growth performance, nonspecific immunity, pathogen resistance and body composition of orange-spotted grouper (Epinephelus coioides H.)

This study investigated the effects of levan produced by Bacillus licheniformisFRI MY-55 on growth performance, intestinal count of viable bacteria, immune status, pathogen resistance and body composition of orange-spotted grouper (Epinephelus coioides). Orange-spotted grouper were fed diets supplemented with levan at concentrations of 0 (control), 5.0, 10.0, 25.0 and 50.0gkg(-1) for 12weeks. The final weight and per cent weight gain were significantly higher in the 25.0gkg(-1) levan-supplemented group than in the control group (p<0.05). All levan-supplemented diets significantly decreased the count of total viable aerobic bacteria and Vibrio spp. in the intestines of groupers (p<0.05). Serum total protein levels, globulin levels, lysozyme activity and survival rate of orange-spotted grouper after challenge with V. harveyi were significantly higher in the 25.0gkg(-1) levan-supplemented group than in the control group (p<0.05). This study also found that the 10.0, 25.0 and 50.0gkg(-1) levan-supplemented diets significantly increased the crude protein level in the body composition of orange-spotted grouper. Overall, the results of this study indicate that dietary levan (25.0gkg(-1)) could be an effective method for enhancing the growth performance and disease resistance in orange-spotted grouper.