THE USE OF ENVIRONMENTALLY-SAFE POLUMS IN AQUACULTURE

Introduction. In the conditions of anthropogenic pollution of water, environment-safe drugs and implementing of immunomodulatory drugs are becoming increasingly common. Schemes of their use in fisheries are being developed. The article presents and analyzes the potential use of biologically active additives (BAA), namely probiotics, prebiotics and yeasts, both domestically and internationally produced, in terms of their effect on the fish body. 
Materials and methods of research. Search for literature data on the use of biologically active substances in fish farming, namely probiotics, prebiotics and yeast. 
Research results. Considering the negative impact of prophylactic and therapeutic use of antibiotics in aquaculture, the use of dietary immunostimulants has been proposed as an alternative to antimicrobial drugs. In this sense, functional dietary supplements, including pre-, probiotics and yeasts, are receiving increasing attention as an environmental strategy to improve fish health. 
Probiotics are the objects of comprehensive scientific research and an important product on the world market. The use of probiotics as biocontrol agents in aquaculture is increasing. The benefits of such additives include increased nutritional value, inhibition of pathogens and enhanced immune response by increasing white blood cells and phagocytosis. They improve the quality of the growing environment, protect fish from biological hazards, and modulate physiological processes that ultimately contribute to the health and welfare of fish in aquaculture. Probiotics also enhance growth performance and feed utilization in aquatic animals by increasing the activity of digestive enzymes. 
The beneficial effects of prebiotics are due to by-products resulting from the fermentation of intestinal commensal bacteria. Among the many health benefits attributed to prebiotics is the modulation of the immune system. They directly enhance the innate immune response, including activation of phagocytosis, neutrophils, alternative complement system, and increased lysozyme activity. 
Another environmentally friendly product that has been proposed as a dietary supplement is yeasts. Research on yeast products in fish diets has focused on their role in nutritional and functional supplements that contribute to the immune responses and gut health of fish. 
Conclusions. Various studies of pro- and prebiotics in fish have shown the following results: effects on growth, gut microbiota, resistance to pathogenic bacteria and parameters of innate immunity such as alternative complement activity (ACH50), lysozyme activity, natural hemagglutination activity, respiratory burst, superoxide dismutase activity and phagocytic activity.All the above studies demonstrate that the addition of nutritional supplements to feed, such as immunostimulants, is an alternative method for the prevention and control of various diseases in aquaculture.