[ AQUACULTURE ] Probiotic microorganisms support aquaculture
Preventive health protection and thriving fish Pre-, pro-, syn- and postbiotics have been increasingly used in aquaculture for some time in order to strengthen the immune system of fish, improve their health and reduce the use of drugs in cases of illness. What kind of substances are they, what are the mechanisms by which they work and most important of all – do they really help?
Substances that influence the so-called microbiome are the subject of particular interest. This term is derived from the Greek words “mikrós” for small and “bios” for life, and it means the totality of all of the microorganisms that naturally live on and in fish and other 22
Olivier Decamp
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n Regulation (EU) No 37/2010, fish are described as “minor species”, for which only a limited number of veterinary preparations are officially approved. This shortage of therapies makes it very difficult for aquaculture operations to effectively treat these animals in case of illness in fish stock. Veterinarians may repurpose standard commercial antibiotics for use in fish, but this is only permissible if a risk to the health of people and animals can be ruled out and a waiting period of at least 28 days until the fish are marketed is complied with. In addition to impacts on growth and possible fish losses due to disease, the affected companies consequently also suffer financial losses due to delayed harvesting, which can significantly disrupt the rhythm of breeding cycles. For these reasons, more and more companies are turning to preventive measures that strengthen the well-being and condition of the fish, thus preventing diseases.
Prebiotics stimulate the activity of bacteria naturally occurring in the intestines thereby strengthening the immune system and rendering the fish less vulnerable to pathogens.
multicellular organisms. Most microorganisms live in the digestive tract as intestinal flora. We now know, however, that many bacteria also live on the surface of the skin (skin flora) and mucous membranes of the body. Some microbiome organisms are only commensals. This means that they live alongside their host fish without discernibly harming or particularly benefiting them. However, a much larger number of microorganisms have developed a symbiotic relationship with their host during the process of evolution, which is manifested in complex, multilayered
relationships at the level of metabolic processes. For example, the intestinal microbiome contributes to increasing the value of nutrients consumed. It synthesizes vitamins that are important for life, produces short-chain fatty acids that positively influence the intestinal environment, supports the breaking down of food components that are difficult to digest and fights inflammation. Also, most of the immune cells of the body are found in the intestines, and their function is regulated by the useful symbiotic bacteria in the intestines.
The intestinal microbiome influences fish health The extent to which microbiota influence the metabolism, the effectiveness of the immune system and the physiological performance of fish has long been underestimated. However, the results of recent research have significantly advanced our understanding of the links between changes in the intestinal microbiome and chronic inflammatory illnesses. Any measures that prevent negative shifts in the species composition or number of bacteria could
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