Aquaculture is the world’s fastest growing food production sector. However, fish culture is currently suffering from serious losses due to infectious diseases. The use of antimicrobial drugs, pesticides and disinfectant in aquaculture disease prevention and growth promotion has led to the evolution of resistant strains of bacteria. Thus, the research into the use of probiotics for aquaculture is increasing with the demand for environment – friendly sustainable aquaculture. The benefits of such supplements include improved feed value, enzymatic contribution to digestion, and inhibition of pathogenic microorganisms, anti-mutagenic and anti-carcinogenic activity, and increased immune response. These probiotics are harmless bacteria that help the well being of the host animal and contribute, directly or indirectly to protect the host animal against harmful bacterial pathogens. The use of probiotics in aquaculture has got popularity due to the fact that gastrointestinal microbiota of aquatic organisms has been poorly characterized, and their effects are not studied extensively.
Why is there still doubt?
Although there is experimental evidence that the prophylactic use of beneficial bacteria can improve health and performance of cultured aquatic species, there are still some doubts. Results can be affected by improper management methods and product quality, such as:
• incorrect application methods.
(e. g. simultaneous use of chemicals or antibiotics).
• incorrect claims of probiotics, which can´t be fulfilled
(e. g. for white spot syndrome).
• too low bacterial concentrations.
(colony forming units should be above 108/g).
• poor bacterial stability during production and storage.
There is plenty of evidence that probiotics supplemented in feed and water are effective in aquaculture application. However, the success of probiotic supplementations depends on the strains, concentrations and management used. Effective probiotics are based on selected strains and controlled production conditions. Poor results are many times related to low-quality and inadequate probiotics.
It has been shown that well-defined probiotic strains, e. g. Enterococcus faecium, are able to reduce pathogenic bacteria, thus improving gut health, and enhancing performance and efficiency in production of aquatic species.
Microscopic pictures (1000-fold magnification) of Vibrio harveyi, Yersinia ruckeri, Streptococcus agalactiae and Aeromons veronii.
Backyard production of probiotics.
There are many shops all over the country, marketing different types of feed and water probiotics (popular one is VC-7) for shrimp hatcheries and farming. A specific amount can be used on trial basis to realize effectiveness of the products before regular use.