The current status and future focus of probiotic and prebiotic applications for salmonids

Salmonids are an important contributor to fish production in many countries. Concerted research efforts have concentrated on optimising production with eco-friendly alternatives to the therapeutic use of antimicrobials. Probiotics and prebiotics offer potential alternatives by providing benefits to the host primarily via the direct or indirect modulation of the gut microbiota. Suggested modes of action resulting from increased favourable bacteria (e.g. lactic acid bacteria and certain Bacillus spp.) in the gastrointestinal (GI) tract include the production of inhibitory compounds, competition with potential pathogens, inhibition of virulence gene expression, enhancing the immune response, improved gastric morphology and aiding digestive function. The application of probiotics and prebiotics may therefore result in elevated health status, improved disease resistance, growth performance, body composition, reduced malformations and improved gut morphology and microbial balance. Current research demonstrates successful proof of these concepts and a foundation for applications in salmonid aquaculture. However, application strategies applied in current studies are varied and often impractical at industrial level farming: thus, it is difficult to plan an effective feeding strategy for commercial level applications. Future studies should focus on providing practical industrial scale applications. Additionally, from a scientific perspective we must have a better understanding of the mucosal-bacterial interactions which mediate the host benefits in order to achieve optimal utilisation. (c) 2010 Elsevier B.V. All rights reserved.