Effects of dietary prebiotics on growth performance, immune response and intestinal morphology of red drum ( Sciaenops ocellatus)

Abstract

An 8-week feeding trial was conducted with juvenile red drum to evaluate four different prebiotics: fructooligosaccharides (FOS) in the form of inulin, galactooligosaccharides (GOS), Bio-MOS ®, containing mannanoligosaccharides (MOS) derived from yeast, and Previda™ containing galacto-gluco-mannans from hemicellulose extract. Each prebiotic was added at a level of 10 g kg −1 to the basal diet which was formulated to contain 41% protein and 10% lipid. Each diet was randomly assigned to three aquaria and fed twice daily to apparent satiation. Fish fed the diet containing Previda™ had significantly higher ( P < 0.05) weight gain than fish fed the basal diet and the one supplemented with Bio-MOS ®. Feed efficiency and protein efficiency ratio of fish fed the various diets were not significantly different ( P > 0.05), although fish fed the basal diet had the lowest values. Fish fed the Bio-MOS ® diet had lower survival than fish fed the other diets. Hepatosomatic index, muscle ratio and condition factor were not affected by the dietary treatments. Fish fed the FOS diet had a significantly lower neutrophil oxidative radical production than fish fed the other diets. However, serum lysozyme activity was significantly lower ( P < 0.05) in fish fed the basal diet compared with those fed the diets supplemented with prebiotics. Quantitative changes in the ultrastructural characteristics of the gastrointestinal tract of red drum fed the various diets were evaluated using histological methods. Fold height and enterocyte height in pyloric caeca and proximal, mid- and distal intestines were not significantly affected by diet. However, microvilli heights in pyloric caeca, proximal and mid-intestine were significantly increased by the supplementation with prebiotics. In this experiment, Previda™ supplementation resulted in significant improvements in growth performance and immunological responses, even as compared to other commercially available prebiotics. Because prebiotic supplementation may result in enhancement of different performance indicators in various fish species, tailored evaluations are recommended before suggesting specific prebiotic strategies.