Aquaculture industry is one of the fastest growing food producing sectors but easily causes economic loss due to exposure to stressful conditions, environmental issues, and diseases. Therefore, a proper and a sustainable way to manage these factors is needed. Antibiotics have been used by farmers for a long time in aquaculture which contribute towards the resistance among bacteria due to mutation in genes which cause adverse effects on aquatic animals and environment. Therefore, an eco-friendly measure which is the use of probiotics has replaced antibiotics with its ability to control the pathogenic spread among aquatic species.
Probiotics consist of live microorganisms that need to be administered in proper amounts and will provide a health benefit to the host. Probiotics have these few criteria that makes it a proper supplement compared to antibiotics. It is a microorganism (bacteria, algae or fungi) but non-pathogenic and free from any side effects, have beneficial activity and also need to survive the gastrointestinal tract of the host. Besides, it should be in an adequate number of viable cells to provide the health benefit and compatible with product matrix, processing, and storage conditions to maintain the desired properties (Collado et al. 2010)
Figure 1. The probiotic can be applied to food with proper amount for significant result
In aquaculture, application of probiotics depends on the reason for using it. If it is to use for only one purpose then a specific probiotic might be a good choice. But, if it is used for many purposes then multispecies and multi-strain probiotic culture shows increased protection against infection (Kesarcodi-Watson et al. 2012). However, the multi-strain probiotics seem to be more expensive compared to single strain. Hence, understanding the purpose of dosing a probiotic is really important to choose proper products. Probiotics should be applied differently depending on the products. It can be directly added into culture water, as water additives, an immersion method of application, bathed in bacterial suspension. The time duration for dosing the probiotics is also different however prolonged exposure would enhance immune suppression of cultured animals.
Since the probiotic aims to eliminate pathogens, therefore it has different methods to destroy the pathogens. First, through competitive exclusion the probiotic competes with pathogens for space, oxygen, energy and nutrients. Therefore, the pathogen that is attached to the mucosal membrane of the gastrointestinal tract of the host to cause disease cannot longer be attached to the receptor (JL. Balcazar. 2006). Second, through immunomodulation, probiotics the immune system of the hosts will be stimulated and increase activity of antibodies and all other factors that improve immunity against pathogens. Third, probiotics have the ability to produce inhibitory substances such as bactericidal, or bacteriostatic effects on other organisms. These substances will help to prevent the proliferation of the pathogenic organism in the host. There are many more modes of action performed by probiotics that tell the effectiveness of probiotics against diseases (Zorriehahra et al. 2016)
Probiotics applied in aquaculture serve for different purposes, such as, to inhibit the pathogens, to improve nutrient digestibility, to improve water quality. The effectiveness of probiotics is acknowledged by scientists around the world. Thus, it depends on the farmers to choose a proper and suitable probiotic to be used in the farm.
Collado, Maria Carmen, Miguel Gueimonde, and Seppo Salminen. "Probiotics in adhesion of pathogens: mechanisms of action." Bioactive Foods in Promoting Health. Academic Press, 2010. 353-370
Balcazar JL, de Blas I, Ruiz-Zarzuela I, Cunningham D, Vendrell D, Muzquiz JL. 2006. The role of probiotics in aquaculture. Vet Microbiol. 114:173186.
Zorriehzahra, Mohammad Jalil, et al. "Probiotics as beneficial microbes in aquaculture: an update on their multiple modes of action: a review." Veterinary Quarterly 36.4 (2016): 228-241
Kesarcodi-Watson, Aditya, et al. "Protective effect of four potential probiotics against pathogen-challenge of the larvae of three bivalves: Pacific oyster (Crassostrea gigas), flat oyster (Ostrea edulis) and scallop (Pecten maximus)." Aquaculture 344 (2012): 29-34.