the current development of the aquaculture industry, an increase in
problems and challenges arises, including a widespread occurrence of
diseases, such as parasitic infestations, bacterial and viral
infections, writes Elisabeth Mayer, Technical Manager, Biomin.
Currently, there is growing
interest in the use of beneficial bacteria, probiotics, as an
alternative strategy to antimicrobial compounds. These naturally
occurring live microorganisms can improve growth and survival of fish
A diverse range of beneficial bacteria is used as probiotics in
aquaculture. Their selection and ability to thrive in the gut play a key
role on the success of its application. The mode of action of
probiotics include competitive exclusion of pathogenic microorganisms
based on mechanisms like production of bactericidal substances,
competition with pathogenic bacteria for nutrients and intestinal
adhesion sites and modulation of the immune system. Ultimately,
probiotics should contribute to efficient production in a sustainable
way, promoting healthy and robust animals (Brittain et al., 2002).
Disease prevention and control in aquaculture are now priority research
topics. This article reports on in vivo trials using beneficial strains
as a probiotic feed additive in cultured aquatic species.
Probiotic inclusion in fish feed
Increased stocking densities in intensive fish
production systems lead to more challenging production conditions. This
brings the need for solutions focusing on improving fish performance and
survival in a sustainable way. Several studies have demonstrated the
efficacy and certain mechanisms of action of probiotics included in fish
Adhesion and colonisation of the mucosal surfaces are possible
protective mechanisms against pathogens through competition for binding
sites and nutrients (Westerdahl et al., 1991). In a trial conducted by
Kidchakan (2006) of the Prince of Songkla University, colonisation of
the intestine was investigated with a commercial probiotic product
containing Enterococcus faecium (AquaStar®, BIOMIN GmbH, Austria) in
In this study it was shown that the probiotic E. faecium colonised the
gut and it was even detected in the gut and faeces after 10 days of the
product administration (Table 1). Different lactobacilli have reduced
the adhesion of A. salmonicida, C. piscicola and Yersinia ruckeri to
intestinal mucus of rainbow trout (Balcazar et al., 2006).
Chang and Liu (2002) showed that survival rates of
European eels fed with Enterococcus faecium were significantly higher
than in the control groups after being challenged with Edwardsiella
More possible benefits for fish linked to the administration of
probiotics have been suggested: B. subtilis and B. licheniformis fed
fish displayed a significant improvement of feed conversion ratio (FCR),
specific growth rate (SGR) and protein efficiency ratio (Merrifield et
al., 2009). Other protective mechanisms of probiotics against pathogens
are production of inhibitory compounds with antibacterial activities and
effects on the immune responses, such as modulation of the white blood
In a recent study conducted by BIOMIN (2010) the effects of dietary
application of probiotics on health and growth performance of Tra
catfish were investigated.
Two different multi-species probiotic products, AquaStar® Growout
(Bacillus sp., Enterococcus sp., Lactobacillus sp., Pediococcus sp.,
colongy forming units (CFU) one multiplied by 109/g) and AquaStar®
Shield (Bacillus sp., CFU one multiplied by 109/g + cell wall fragments)
Groups of 40 fish (66.3 ± 0.3 g) were stocked into 300 L tanks and fed
to satiation three times daily during an eight week period.
The experiment was set up using five treatments and five replicates per
treatment with both probiotics tested at two inclusion levels (AquaStar®
Growout one g/kg and three g/kg, AquaStar® Shield one g/kg and two g/kg
At the end of the trial blood samples from three fish per tank were
taken for determination of haematological parameters (trombocytes,
lymphocytes, monocytes and polymorphonuclear leucocytes). Dietary
application of probiotics had a positive effect on several fish
performance parameters. These effects were dose dependent and varied
between the two probiotics.
Feed application of AquaStar® Growout at three g/kg and AquaStar® Shield
at one g/kg resulted in increased (P < 0.05) weight gains of 12 per
cent and 11 per cent, respectively (Figure 1).
At those inclusion levels, these probiotics were also effective in
improving FCR by 10 per cent and nine per cent, respectively, when
compared to the control. Application of AquaStar® Growout at one g/kg
and AquaStar® Shield at two g/kg improved fish performance but was not
significant (P > 0.05) when compared to control.
The haematological parameters shown in Table 2
indicate that AquaStar® Growout (one g/kg) induced a significant
reduction (20 per cent) in trombocytes and an increase (30 per cent) in
lymphocytes when compared to the other treatments. Levels of monocytes
and polymorphonuclear leucocytes were not affected by the treatments.
Results showed that probiotic application in fish
feed can be an effective solution to improve growth performance and
health status. Moreover, dosage application should be adapted to the
composition of bacterial strains used.
Probiotic inclusion in shrimp feed
In the economically important panaeid shrimp, Vibrio
species have become a major constraint on production and trade during
the past two decades. They are responsible for several diseases and
mortalities of up to 100 per cent, causing global losses of around US$
There is already experimental evidence that the prophylactic use of
probiotics to control pathogens by competitive exclusion can improve
health and performance of cultured shrimp. The positive impact of added
probiotics on bacterial ecology in shrimp gut was shown in a trial
conducted with white shrimp (Litopenaeus vannamei).
A multi-strain probiotic mixture containing E. faecium (AquaStar®,
BIOMIN GmbH, Austria) fed to shrimp 5 times daily during a six week
period at an inclusion rate of five g/kg feed has reduced the total
number of Vibrio spp. found in the hepatopancreas and intestine of
shrimp. This evidence showed that probiotic Enterococcus can colonize
the shrimp gut and reduce the number of pathogens through competitive
exclusion (Supamattaya et al., 2005).
Furthermore, the non-specific immune system can be stimulated by
probiotics. Rengpipat et al. (2000) indicated that the use of Bacillus
sp. in tiger shrimp provided disease protection by activating both
cellular and humoral immune defenses.
In a recent study, Jintasataporn et al. (2010) investigated the effect
of AquaStar® Growout (BIOMIN GmbH, Austria) in white shrimp (Litopenaeus
vannamei) production performance parameters. Groups of juvenile white
shrimp (0.86 ± 0.31 g) were stocked into 240 L glass aquaria, at a
density of about 100 shrimp/m², and fed four times daily for eight
A commercial type diet was used as a control. AquaStar® Growout was supplemented to the feed at an inclusion rate of three g/kg.
Considering the shrimp production per square meter,
the results in Table 3 and Figure 2 show that shrimp production was
improved by 9.40 per cent in the group applied with AquaStar® Growout
compared to the control. The analysis regarding the CFU of LAB showed
significantly (P < 0.05) higher levels in the probiotic group. Lactic
acid can enhance growth performance due to optimum acidic conditions in
the digestive system which promote nutrient digestion and absorption.
Maintaining the balance of critical parameters is a
fundamental requirement for successful aquaculture. In order to
withstand the high stocking densities in shrimp and fish production
probiotics are a promising feed additive to stimulate animal growth and
secure a low disease response. The data of these studies suggest that
the use of AquaStar® improved survival, growth rates and the general
health status of fish and shrimp while also reducing pathogenic Vibrio
More research effort is needed to secure even better results in the
future. Probiotics have to be extensively investigated in terms of new
bacteria strains, their mechanisms of action, efficacious level of
administration alone or in combination with other natural products with
ascertained health promoting activities (Ringo and Olsen, 2008).
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