Application of multi-species of Bacillus in sea bream larviculture

To date, probiotics can be considered a valid alternative to the use of antibiotics in aquaculture and in particular, in fish larviculture, to prevent high mortality and to improve welfare and promote growth. In the two last decades, many studies reported promising results using a single beneficial bacterial strain in the culture of many finfish species. Looking for innovative ways to improve fish larviculture, we tested a mixture of Bacillus probiotic bacteria in the gilthead sea bream (Sparus aurata) larviculture focusing on their effects on survival, growth and general welfare. The mixture, composed of three Bacillus strains, Bacillus subtilis. Bacillus licheniformis and Bacillus pumilus was provided via rotifers and Artemia nauplia and added to the water (group 1) or supplied exclusively via live prey (group 2). The Bacillus mixture significantly increased growth in terms of standard length and body weight in both experimental groups, at larval and juvenile stages, 47 and 75 days after hatching, respectively, with the highest values obtained from Group 2 treatment. In addition, the expression of genes involved in growth metabolism (Insulin-like Growth Factors I and Myostatin) and animal welfare (70 KDa-Heat Shock Protein and Glucocorticoid Receptor) were analysed. The morphometric analysis was supported by molecular results which clearly evidenced higher expression of IGFI and lower levels of myostatin in groups fed on probiotics. In addition, a better tolerance to farming conditions was also found as evidenced by the lower expression of HSP70 and Glucocorticoid Receptor, suggesting beneficial effects of the supplied Bacillus mixture on fish welfare. The data generated in this study provide scientific and technical support for the implementation of sustainable development of sea bream aquaculture. (C) 2010 Elsevier B.V. All rights reserved.