Four years ago, the early mortality syndrome (EMS) or acute hepatopancreatic necrosis disease (AHPND) appeared in shrimp farms in Asia. The disease has devastated the shrimp industry in China, Vietnam, Malaysia and Thailand. This disease is caused by a bacterium Vibrio parahaemolyticus which is potentially modified by a bacteriophage agent, causing a toxin secretion (TCP/VIE/3304 report, 2013). In order to prevent this disease, one of the measures taken by the industry is to design specific feeds for the shrimp. Parietal fractions are isolated from yeasts and contain mannan oligosaccharides, beta glucans, chitin and components that are potential immune-stimulants (Ringo et al., 2012), and they have been shown to prevent bacterial infections. The expertise of Phileo Lesaffre Animal Care business has specifically designed parietal fractions with known and consistent concentrations of these components using a specific strain and optimised production processes including drying. The aim of this study was two-fold: first to determine the optimum dosages for the parietal fraction Safmannan® to increase the survival of shrimp against the AHPND, and second to test if a short immune-stimulation of two weeks was sufficient