Fermentation of Feed Ingredients as Potential Strategy to Improve Health Status and Reduce Opportunistic Pathogens in Fish Farming

The rapid increase in fish farming has been affected by outbreak of diseases and erratic feed costs. These challenges have stimulated increase in the use of antibiotics to rear fish. Unfortunately, excessive use of antibiotics inhibits or kills beneficial gut microbiota and makes antibiotic residues to accumulate in fish products, which are harmful for human consumption. The use of biological strategies has therefore, been adopted to improve health status, growth performance and reduce predisposition of fish to diseases. This has become necessary in view of the EU ban on most antibiotics used as growth promoters in animal husbandry due to their roles in the production of antibiotic resistant bacteria. Moreover, use of the natural fermentation process, which utilizes functional and safe microbes to transform large and potentially harmful chemical constituents in fish feed to less harmful or safe states have been contemplated in aquaculture. In the present review, lactic acid bacteria (LAB) activity during feed fermentation to mediate positive effects in farmed fish is highlighted, including; modulation of gastrointestinal pH, production of bacteriocins, competitive inhibition and translocation of pathogenic bacteria in the GIT. Other potentials of fermentation to promote feed efficiency and growth performance in fish are also discussed.