মৎস্য চাষে Probiotic কেন ব্যাবহার করবেন

Application & Benefits of Probiotic in Aquaculture

The word Probiotic was first introduced by to describe “substances secreted by one microorganism that stimulate the growth of another”. The name Probiotic comes from the Greek “pro bios” which means “for life”.

In the field of aquaculture, the concept of Probiotic should be defined taking into account other influencing factors that differentiate it from terrestrial Probiotics.

Extend this definition as “a living microbial complement that has a beneficial effect in the host or environment, ensuring a better utilization of the feed or improving the nutritional value, improving the host’s response against a disease, or by improving the quality of its environment. 

1. Pond treatment

2. Water treatment

3. Feed additive

Reduction in Capital outlay:

1. Reduction in chemical input

2. Better disease control.

3. Feed cost reduction.

Increase in yield:

Size and numbers.

Improvement in quality:

1. Better shine.

2. No earthy smell.

3. Better shelf life.

Benefits:

1.  Reduces the capital outlay drastically.

2.  Facilitates the culture of fish and prawns without chemicals.

3.  It reduces the quantity of sludge produced.

4.  It eliminates Ammonia, Methane and Hydrogen sulphide which are    

     common in fish/prawn cultivation.

5.  It helps to keep water clean and hence does not require repeated   

     Changing.

6.  Helps in suppressing algal colonies from bodies of fish/prawns, thus

     giving better growth.

7.  Fish and prawns produced are of higher quality and quantity.

8.  Feed conversion ratio (FCR) improves

9.  Mortality of fish and prawns can be reduced significantly.

Overall beneficial effects of Probiotic in aquaculture. Green arrow indicates additive effects. Red lines indicate inhibitory effect.

Modes of actions

Colonization capacity

Antagonistic activity

Enhance immune responses

Elevate health status and disease resistance

Improve water quality

Improve growth and survival rate

1. Competition for space

Many of the pathogenic bacteria require attachment to the mucosal layer of the host gastrointestinal tract to initiate the development of a disease.

 An important mechanism of action in probiotic bacteria is competition for adhesion sites, also known as ‘competitive exclusion’. The ability of bacteria to colonize the gut and adhere to the epithelial surface and consequently interfere with the adhesion of pathogens is a desirable criterion in the selection of probiotics..

2. Production of inhibitory substances

Probiotic bacteria produce substances with bactericidal or bacteriostatic effects on other microbial populations such as bacteriocins, hydrogen peroxide, siderophores, lysozymes, proteases, among many others. 

2.1. Antibacterial activity

2.2. Antiviral activity

2.3. Antifungal activity

3. Competition for chemicals or available energy

 Probiotic group lactic acid bacteria, consume the nutrients that are essential for the growth of a number of pathogens.

4. Improving the water quality

Application of Gram-positive bacteria, such as Bacillus spp.,is beneficial in improving the quality of the water system. Bacillus spp.have a more efficient ability in converting organic matter into carbon dioxide in comparison to the Gram-negative bacteria, which converts a greater proportion of organic matter into bacterial biomass or slime. 

Probiotic bacteria possess significant algicidal effect as well particularly on several species of microalgae, Ammonia and nitrite toxicity can be eliminated by the application of nitrifying cultures into the fish environment.  

Probiotics are beneficial as they can increase microbial species’ composition in the water and modify its quality, The temperature, pH, dissolved oxygen, NH₃ and H₂S in rearing water were found to be of higher quality when probiotics were added, hence maintaining a positively healthy environment for shrimp and prawn larval in green water system.  

5. Nutrients and enzymatic contribution

Some microorganisms have a positive effect in the digestive processes of aquatic animals.  It has been shown that some bacteria contribute in the digestion process by producing extracellular enzymes, such as proteases, lipases, as well as growth-promoting factors.

Probiotics, especially from Bacteroides and Clostridium sp., are capable of supplying vitamins, fatty acids and essential amino acids to the host. Gnotobiotic oyster larvae (Crassostrea gigas), fed with auxenic algae (Isochrysis galbana) supplemented with a bacterial strain CA2, showed not only improved growth performance but efficient nutrient utilization as well.

6. Interference of quorum sensing

Quorum sensing (QS) is defined as the regulation of gene expression in response to fluctuations in cell-population density. Many bacteria are using this system to communicate and regulate a diverse array of physiological activities.

7. Immunomodulation

7.1. Fish

Probiotics by stimulation of immune system of hosts, including the stimulation of pro-inflammatory cytokines on the activity of immune cells, increasing the phagocytic activity of leucocytes,, increasing the levels of antibodies, acid phosphatase, lysozymes, complement, cytokines,  IL-10 and transforming growth factor, and antimicrobial peptides,  and also, by improving the intestinal microbial balance, inhibiting the colonization of fish pathogens in the digestive tract, producing of inhibitory compounds such as bacteriocins, sideropheres, lysozymes, proteases, hydrogen peroxides,   increasing the digestive enzymes activity,  and by producing of fatty acids, vitamins, and essential amino acids that are useful for lactic acid bacteria could improve the growth performance, immune system and increased resistance on common pathogens in fish.

7.2. Shrimp

Use of probiotics in different species of shrimps has improved the innate immunity (natural or non-specific immunity).

7.3. Immunomodulation of the gut immune system

The immune system of the gut is related to gut-associated lymphoid tissue (GALT) and there are some differences in respect of Peyer's patches, secretory IgA and antigen-transporting M cells in the intestine of piscine and mammal gut immune system.

7.4. Amelioration of the effects of stress

Stress might be regarded as a physical or chemical agent causing reactions that may result in disease and death. Any change in water parameters may have a side effect on the physiological and behavioral aspect of aquatic animals. Many harmful agents for fish exist in their environment like the water, soil, air or even their own body.

Conclusion and future perspectives

Use of probiotics is an effective alternative sustainable source of beneficial microbes with bactericidal or bacteriostatic effect on pathogenic bacteria, with anti-bacterial, anti-viral and anti-fungal activity, immunomodulatory capabilities of promoting health and welfare to improve the growth performance, augment the immune system, disruption of QS as a new anti-infective strategy, ameliorate the harmful effects of oxidative stress factors and increased resistance for common pathogens in fishes for controlling potential fish pathogens.

An interactive approach among academicians, scientists, producers and fish sector owners is required to focus and explore the specific aspects of bacteria–host interactions conferring the possible favorable changes in diverse immune responses elicited by different bacterial strains in order to propose clinically effective, bacteria-based strategies to promote the health, production and economic growth of the aquaculture industry.

Probiotic formulation should be viable on large scale at low operational cost. They should not be treated as ‘elixir of life’, rather they should be used as supplement to balance the diet to avail and maintain the sound health free of infections and disease-causing microorganisms.

The present review has summarized the importance of potential probiotics and their future perspectives in fastest growing food production sector of aquaculture industry.