Abstract
Probiotics, which are regarded as micro-organisms administered orally leading to health benefits, are used extensively in aquaculture for disease control, notably against bacterial diseases. In contrast to use with terrestrial animals where lactic-acid producing bacteria dominate, a diverse range of micro-organisms including Gram-negative and Gram-positive bacteria have been considered in aquaculture. The source of these organisms is often the digestive tract of the host animal. The mode of action includes competitive exclusion and immunomodulation. Probiotics may also improve appetite and lead to enhanced growth and better feed conversion. (C) 2013 Elsevier B.V. All rights reserved.