Effects of dietary prebiotics on the growth, feed efficiency and non-specific immunity of juvenile red drum Sciaenops ocellatus fed soybean-based diets

Previous work has demonstrated several benefits of dietary prebiotics for fish. Here, we report the effects of added dietary fructooligosaccharide (FOS), mannanoligosaccharide (MOS), transgalactooligosaccharide (TOS) and GroBiotic (R)-A (GBA) on the weight gain, feed efficiency and non-specific immunity of juvenile red drum fed soybean meal (SBM)-based diets, in brackish water at 25 +/- 1 degrees C. Test diets incorporated FOS, MOS, TOS or GBA at 10 g kg-1 in place of cellulose in a basal diet with 40% crude protein, half from SBM and half from fishmeal. After a 4-week feeding period, experimental fish were challenged by exposure to Amyloodinium ocellatum, after which growth and survival were monitored for 2 more weeks. Feed efficiency, serum lysozyme and intracellular superoxide anion production were significantly (P < 0.05) enhanced by prebiotic supplementation. Likewise, survival after A. ocellatum exposure was significantly higher for fish fed GBA, MOS and TOS (87%, 84% and 78%) versus 58% for fish fed either the FOS or the basal diet. Taken together, these results indicate that inclusion of several prebiotics at 10 g kg-1 of the diet is adequate to improve the feed efficiency of red drum as well as to enhance disease protection.