Integrated control of fish metabolism, wellbeing and reproduction: The role of probiotic

In the last decades, attempts to sustain an environmental friendly aquaculture have encouraged the use of beneficial bacterial, including probiotics, as feed enrichment. The use of probiotics has been extended far beyond finfish aquaculture, since they have been added to experimental and/or commercial diets formulated for invertebrates including Crustaceans, molluscs, echinoderms. The results so far obtained largely demonstrated beneficial effects of probiotics on fish growth, digestive function, immune system modulation, stress resistance and fecundity. Many studies demonstrated the potentiality of probiotic administration to elevate the fish innate defense mechanisms, hence improving survival following exposure to a number of pathogens. Benefits are driven, at least in part, by the modulation of the host microbiota. Probiotic “colonization” is the first key process responsible for increasing welfare. The review will summarize the effects of microbiota changes on welfare, growth and reproduction of both ornamental and commercial species. Reproduction is an energy-costly process that can be successfully faced only when sufficient energy stores are available. Particular emphasis will be given to the effect of probiotics on the interplay between metabolism and reproduction. A number of central energy sensors, hypothalamic neuropeptides, and several peripheral molecular mediators have been implicated in the regulation of the delicate interaction connecting the two processes. The last part of the review condenses recent findings regarding the positive effects of probiotic administration on fish gonads, which deeply support their role towards reproduction, mainly achieved on zebrafish. Indeed, the results presented scientifically support and strongly encourage the large scale use of probiotics in aquaculture practices, suggesting avoidance of pharmaceuticals use. If that becomes well established, a better quality, both health- and environment-wise, could be achieved and supplied to consumers. Probiotic improvement of growth, wellbeing and reproduction.