Today the world’s economic growth facing a lot of challenges due to many factors like disease outbreaks, population, climatic changes, productivity issues, etc., Agriculture, livestock production, and aquaculture industries are playing a vital role in the development and strengthening process of economic growth and food supply chain of a nation and the world. Among the food sectors, aquaculture is one of the most promising, and consistently growing industries. In this topic, we are going to discuss the factors that help the aquaculture industry to get optimum production, and how to get healthier aquaculture outputs to ensure a quality food supply chain. It is essential to produce healthier animals without compromise the quality to meet the rapidly increasing population as well as feeding them and fulfil their nutritional requirement. The production of healthier aquatic animals means without any disease while and after growing, harvesting, even until to reach consumer is more important in the livelihood. The livestock and aquaculture industries are practicing many strategies to manage, protect, and cure animals from disease outbreak.
Application of antibiotics, antibacterial chemicals, herbals, vaccines, and probiotics are common practices in the aquaculture industries. Due to the concern of antibiotic and antibacterial chemical residues and pathogen resistance development, the agriculturist is keep emphasizes alternate methods to consider the benefits of aquatic animals as well as environment friendly. Among those, probiotics are the top most additive in feed mills as well as in the day-to-day farm-level application, because of their beneficial points of eco-friendly, non-GMO, no residual effect, no side effects, immunomodulation, etc. Probiotics are classified as mainly two types which are feed supplement probiotic and water probiotics. What are Probiotics? There are many descriptions around the world, the most suitable and accepted one is as per FAO, “Probiotic is a live microorganism which administered in adequate amounts confer a health benefit to the host.” The meaning of probiotics is, “Pro” and “bios” stand for " for life.”
What should be the characteristic of Probiotics?
A beneficial effect to the host especially helps to fights against the disease-causing pathogens
Should not cause any harmful effects to the host and also to human beings as an end-user.
The probiotic should be stable and viable in all industrial processes from lab culture to downstream, even at storage until to deliver to the animals.
Probiotics should be viable in different environmental conditions in the animal intestine (should be viable at a broad range of pH and bile salt).
Should be survivable and colonizable in the gut.
Probiotic microbes should have a strong capability to control and inhibit the growth of pathogen microbes by its secretion components.
Currently, probiotics are being widely used in the aquaculture industries in different forms and methods and their beneficial claims: Probiotics are currently available in the market, mainly in three forms such as powder, liquid, and gel. The powder itself has different forms like fine powder, flakes, granules, and micro-pellets as feed and water probiotics. Nowadays, technologies such as encapsulation or top-coating methods are available to support and enhance the survival rate of probiotics during feed processing and administration to the animals. In the aquaculture industry, different forms of probiotics are being used in feed mills, hatcheries, farms, and breeding units. For example, powder form is mostly being used in the feed mills and less percentage of liquid or gel/semi-solids are being used in the feed mill but mostly post-processing (prepared feed) as a spray method, due to technology limitation and additional capital investment. But in this method, the survival rate of probiotics is high compared to the direct application into the feed mixer. Liquid or semi-solid forms are mostly used in ponds in the day-to-day practice of aquaculture farms as a top-coating for health management, optimum performance, and profit outcome.
The beneficial claim of Probiotics in Aquaculture, especially fish and shrimps, the immune system improves by probiotic microbes by increasing the Ig level in the blood serum and immune molecules, which helps the aquatic animals to minimize colonization of pathogenic microbes. Probioticsdirectly linked with the immune system to induce an immune response by enhancing the production of antibodies; boost-up macrophages and T-cell proliferation, and also keep the immunity in active condition in critical situations. Once live beneficial microorganisms entered into the aquatic animals(e.g., fish and shrimp) make colonization in the gut, and create competition to the pathogenic microorganisms. Once after the colonization in the intestine, probiotics involve in the secretion of enzymes, organic acid, and some more metabolites of vitamin, amino acid, etc., which are more helpful and ensure the aquatic animal’s optimum digestion. Those secretions help the aquaculture animals as a stress-free, healthier, optimum nutritional absorption, which ensures the farmers the maximum productivity, better FCR, and high profit. Regular administration of probiotics as a single or combination of different probiotics will regulate the intestine’s biomass and help to maintain the optimum morphology of the intestine, and help better structure of villi. Probiotics do a vital role in the intestine to utilize the carbohydrates by the fermentation process and convert it as short-chain fatty acid which is the main component for the development of villi structure.
Present strategy of probiotic application in aquaculture
As per the statistical report, aquaculture consumption per capita estimation for 2020 to 2030 is 21-22 kg in the world, which is 10% higher than the current per capita. Due to high demand, pressure fall on the aquaculture producer, which automatically leads to disease out-break from the high-density practice, pond management, drainage from the used water from the pond. Prevention and disease management simultaneously will increase the consumption of antimicrobial and antibiotic chemical residuals, which leads to disease-resistant development in pathogenic microorganisms. Alternate to chemicals and antibiotics, probiotics can improve disease resistance, growth performance, feed conversion ratio (FCR), and stress resistance in aquaculture organisms. The effects of probiotics in aquaculture are not only colonization in the intestinal tract; they also improve health by limiting the growth of pathogens and improve the water quality by controlling the microbial growth and population in the water and bottom settlement of organic solids. Using probiotics is a new concept in aquaculture compare to livestock and poultry, but understanding and acceptance are quicker worldwide. Industrially important disease-spreading pathogens and water quality can be controlled by some probiotic microbes of Lactobacillus spp., Bacillus spp, Saccharomyces spp, etc.
What are probiotics in aquaculture and their benefits?
In the day-to-day practice of aquaculture, different probiotics are being used for different benefits or effects as a single probiotic and blend (from 2 and above). Probiotic microorganisms in the aquaculture markets are Bacillus spp, Enterococcus spp, Lactobacillus spp, Lactococcus spp, Vibrio spp, Rhodopseudomonas spp, Saccharomyces spp, Streptococcus spp, etc. Research showing that an optimum dosage of 107-108 CFU/g has beneficial effects on the host animals, but some studies proved that even higher dosage given significant effects. Continuous addition of probiotics to the host is recommended. At the same time too much inclusion, long-term administration of probiotics can be causing immunosuppression, preferable for 15-21 days administration is better results. Studies are confirming that a combination of probiotic microorganisms of Bacillus spp and Enterococcus with MOS (Mannan Oligosaccharides) or FOS (Fructo Oligosaccharides)has significant beneficial effects of improving growth, FCR, immunity and disease resistance in aquaculture. A nitrogenous component, such as ammonia, nitrite, and nitrate, and H2S gas has been a serious problem in the aquaculture industries, especially in shrimp farms. Some Lactobacillus spp of probiotic vital role in pond application for eliminating the nitrogen issues and controls the pathogen microbes in the shrimp farms. The below table are some examples of probiotics and their disease controls benefits in the aquaculture
Probiotic Microorganism Species/Animal Benefits
Bacillus subtilis Shrimp (Litopenaeusvannami) Inhibit the Vibriosis outbreak
Bacillus megaterium Shrimp improve the resistance to white spot syndrome Virus
Enterococcus faecium Shrimp control Vibrioparahaemolyticus
Bacillus pumilus Tilapia Improve the larval survivalland control Aeromonashydrophila
Lactobacillus acidophilus Tilapia (Nile) Control disease outbreak of Pseudomonads fluorecens
Lactobacillus rhamnosus Fish (Rainbow trout) Improves the disease- resistance to Salmonella
Rhodococcus spp Fish (Rainbow trout) Control the diseaseof Vibrio anguillarum
Saccharomyces cerevisiae Shrimp and Fish Control Vibriosis disease.
Points to consider before select probiotic for aquaculture
• The probiotic microorganism should be on the list of GRAS.
• Should not cause any side or adverse effect on the host animal as well as human.
• The survival rate should be high in the mode of application and storage.
• Make a tangible beneficial effect on the host animal.
• Should not develop any drug resistance, and residual effects.
• Rather than select or use one probiotic, better to go with a combination for a broad range of beneficial effects.
• It should be eco-friendly and user-friendly.
• Probiotics effects based on the dosage, frequency, environmental factors, combination, and animals’ growth stage.
While considering all these points certainly will confirm the beneficial effects to the host animals to ensure the profit and minimize the risk factors in the day-to-day operations in the aquaculture.
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