In India, the steady growth in freshwater aquaculture is led by the recent production of the Pangasius catfish. In fact, Andhra Pradesh, the fifth largest state in the country, is now know as the “Fish Bowl” of India for its rich production of pangasius.

1. March | April 2014
The role of prebiotics in pangasius
production
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3. I
n India, the steady growth in freshwater
aquaculture is led by the recent produc-
tion of the Pangasius catfish. In fact,
Andhra Pradesh, the fifth largest state in
the country, is now know as the “Fish Bowl”
of India for its rich production of pangasius.
Catfish production is the fastest grow-
ing fish farming in the country’s aquaculture
sector; however it appears as the higher the
production increases, the higher the risk for
disease outbreak among the species.
Under intensive production methods and
poor culture management, fish are exposed
to stressful conditions leading to growth
reduction and higher susceptibility to various
diseases. Red disease often occurs during the
change from the dry to rainy season and dur-
ing the flood season.
Signs of Red disease include the fraying
and reddening of fins, and irregular, vari-
ably sized areas of de-pigmentation and red
pigmentation that can develop anywhere on
the body surface, leading to open sores and
ulcers. Infections can occur in any age, but
losses tend to be most severe in fry and small
fingerlings.
Pseudomonas fluorescens, thought to be the
causative agent of the Red disease, or Bacterial
Hemorrhagic Septiciemia disease of pond-
cultured fish, is considered a primary pathogen
of freshwater and opportunistic pathogen for
different fish species grown in marine and
brackish waters worldwide. Clinical symptoms
of the bacteria include darkening of the skin
and hemorrhage in skins and the fins.
According to a study conducted by the
Department of Aquaculture, Bangladesh
Agricultural University (Faruk, Md. A.R. 2008),
the most prevalent symptoms of the Red
disease in pangasius hypophthalmus, are red
spot, followed by anal protusion, tail and fin
rot, pop eye, dropsy and gill rot.
The 100 fish farmers interviewed also
reported other conditions like cotton wool
type lesion, ulceration and white spot, but at
lower rates. Economic losses were estimated
to be 3.6 percent of the farmers’ total yearly
income in fish production due to ill-health.
The successful control of disease in aqua-
culture requires a multifaceted approach,
whereby better management practices are
combined with the use of specially selected
fish stock and adequate nutrition to improve
overall fish health.
In intensive culture systems, improvement
The role of prebiotics in
pangasius production
by Dr Serge Corneillie, general manager, Alltech Japan - Email: scorneillie@alltech.com
table a: the length growth of catfish fry
treatment t1 t2 t3 t4
Initial lengtj (cm) 0.6±0.02a 0.6±0.02a 0.6±0.02a 0.6±0.02a
Final length (cm) 4.24±0.91a 4.39±0.99ab 4.99±1.22b 5.63±1.25c
length gain (cm) 3.83±0.87a 3.97±0.90ab 4.74±1.26b 5.46±1.43c
DlG (cm/day) 0.13±0.03a 0.13±0.03a 0.16±0.04b 0.18±0.05c
SGr (%/day) 6.70±0.76a 6.81±0.66ab 7.30±0.87b 7.72±0.86c
table 1: Culture parameters in trial ponds.
Ponds
Stocking
numbers
area (ha)
Stocking
Density
(no/m2)
Initial
average
body
weight (g)
Days of culture (DoC)
t1 46,600 2 2.33 135 38
t2 25,000 0.8 3.13 80 38
t3 38,450 1.4 2.8 213 37
C1 69,752 2.2 3.1 256 30
C2 69,993 2.2 3.1 194 30
C3 76,251 2.2 3.5 201 28
aactigen™ at 1kg/tonne (applied along with premix in floating feed)
bantibiotic treatment. one at start of trial 4/10/2009 + following treatments at disease outbreak.
note: as this is a field trial, we were limited in controlling some parameters such as initial weight
and days of culture.
10 | InternAtIonAl AquAFeed | March-April 2014
FEATURE

4. of natural health and immunity in fish is
dependent on proper nutrition.
From a commercial perspective, mannan
oligosaccharides (MOS) have been used in
aqua diets for almost 20 years. The return
on investment, based on increased perform-
ance and improvement in efficiency, has
been demonstrated in countless academic
and commercial trials. The major source of
these functional carbohydrates is the cell
wall fraction of bakers’ and brewers’ yeast,
Saccharomyces cerevisiae.
Recently, new data has become available
on a second-generation, purified and more
bioactive fraction derived from a selected
strain of Saccharomyces cerevisiae. This natural
Mannan Rich Fraction of carbohydrate (MRF)
has been shown to block unfavorable organ-
isms from the gut. This carbohydrate supports
nutrient utilisation, maintains digestive function
and enzyme activity, controls inflammation
and reduces the gap between ideal and actual
performance. These mechanisms have been
confirmed using nutrigenomic data. (Note:
The compound is commercially available as
ActigenTM (Alltech Inc) which is a bioactive
fraction derived from yeast cell wall and has
shown favorable results on growth perform-
ance and health status of the pangasius
catfish.)
Indirectly, recent studies have illustrated
the potential to reduce cost of antibiotic
inputs in aquaculture through the improve-
ment of gut health and nutrient absorption
and ultimately a healthy immune status of
the fish.
Gut health and immunity
The gastrointestinal tract is a prominent
part of the immune system.
Microorganisms are kept at bay by an
extensive immune system comprising gut-
associated lymphoid tissue (GALT).
In terrestrial animals including humans, the
microflora of the gastrointestinal tract plays
an important role in affecting nutrition, health
of the host and in the balancing beneficial
and harmful bacteria. A ratio of 80 percent
March-April 2014 | InternAtIonAl AquAFeed | 11
FEATURE
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5. beneficial to 20 percent harmful bacteria is
considered normal.
The bacteria in the water surrounding the
fish are continuously ingested either with the
feed or when the host is drinking, causing a
natural interaction between the microbiota of
the ambient environment and the gut envi-
ronment. If the bacterial challenge exceeds
a certain level, the health of the animal is in
danger, as the animal alone cannot defend
itself sufficiently.
The potential for reducing stress and
enhancing immunity and disease resistance by
nutritional feed additives and functional feed
materials has been demonstrated in warm-
blooded animals.
However, very little work in this area has
been conducted in aquaculture.
Thus, the effects of nutrition and feeding
strategies need to be assessed to develop
economically viable feeds and feeding prac-
tices to optimize growth, improve stress
resistance, immune response and disease
resistance and improve the product quality of
aquaculture species.
However, is this really possible?
The answer is yes, through the pro-
motion of early gut development
with nucleic acids, organic trace
minerals as well as ‘feeding the gut’
to maintain intestinal health.
Recent research
A recent study in Vietnam
examined how to improve the
survival rate of striped catfish
(Pangasianodon hypophthal-
mus) fingerlings by adding rotifers
and Actigen.
The trial, conducted from
June 10 to September 20, 2012,
focused on three diets containing
0.04% Actigen (2nd treatment),
0.08% Actigen (3rd treatment)
and 0.12% Actigen (4th treatment)
and one diet without containing
Actigen (1st treatment) were evaluated.
Rotifers and Actigen addition had positive
results in improving survival rate as well as in
stimulating growth rate of catfish fingerlings.
The survival rate of the fish in the fourth treat-
ment improved approximately 34 percent
comparing to that in the first treatment.
The more concentration of Actigen was
added, the higher survival rate of fish achieved.
Therefore, the average survival rate of
the catfish fingerlings increased from the first
treatment (8.31%), the second treatment
(9.36%), the third treatment (10.13%) and
the fourth treatment (11.16%) (see figure 4.1).
The growth rate of fish also increased when
increasing Actigen concentration added. The
average length and weight of fish at the 30th day
in 1st treatment was 4.24cm and 0.77g, 4.39cm
and 0.82g for fish in 2nd treatment, 4.99cm and
0.93g for fish in 3rd treatment, 5.63cm and 1.08g
for fish in 4th treatment (see figure 4.6).
In another study in India, researchers
looked at the immune competence of
Pangasius hypophthalmus when subjected to
the prebiotic during grow-out in ponds.
This was conducted in a farm located
in Losari, West Godavari District, Andhra
Pradesh, India. The farm contained 30 ponds
of which 20 suffered from higher than normal
outbreaks of disease (see Table 1).
The farm was applying antibiotics
(Enrofloxacin @ 15g/tonne of fish biomass)
to treat disease. As disease outbreaks
became more frequent, the farmer faced
losses from heavy mortalities and increasing
costs of treatments. Researchers selected
three ponds as treatment ponds (T1, T2, T3)
and three control ponds (C1, C2, C3), where
the standard procedure of using antibiotics
was continued.
During the three-month trial, weekly sam-
pling by weighing 100 fish was carried out.
Data recorded included growth rate and
fish mortality (see Table 2 and Figure 1). The
diets used were a standard balanced floating
feed. The treatment diet contained the prebi-
otic at 1kg/tonne of feed.
Fish in the control ponds were fed the
standard balanced floating feed with antibiotic
treatments added at 5g/tonne of fish biomass
for five days in each application.
The researchers concluded that the addi-
tion of the prebiotic helped in reducing the
mortalities and dependence on the antibiot-
ics and also ensured better returns for the
farmer. Based on the above field observations
they concluded that, the use of the prebi-
otic in the extruded feeds will enhance the
complete utilization of feed, thereby leading
to less excretion (less pollution) and higher
profitability for the farmer.
Conclusion
Often it has been hypothesized that fish
invest more energy in immunity than in other
physiological functions.
Moreover, seasonality is thought to act as
an important factor in determining the levels
of fish physiology and immunological activity.
However, the inclusion of certain immune
enhancers can help fish to improve their
immune status and spend less energy on
those defense mechanisms leading to lower
inputs for treating fish.
table 2: Summary of production parameters and inputs used
Ponds
aBW (g)
Initial
aBW (g)
final
Biomass
Increase
(g)
Feed Used
(tonne)
actigen
used (kg)
antibiotic
used (g)
Mortality
(number)
t1 135 470 335 28.01 28.01 - 7
t2 80 447 367 16.52 16.52 - -
t3 213 639 426 29.48 29.48 - -
C1 256 846 590 61.73 - 6.97 350
C2 194 610 416 52.41 - 6.99 500
C3 201 713 512 62.47 - 7.62 275
Figure 1. Growth performance of
pangasius catfish over three months
Figure 2: Survival rate of catfish fry
12 | InternAtIonAl AquAFeed | March-April 2014
FEATURE

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March-April 2014 | InternAtIonAl AquAFeed | 13
FEATURE

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The Role of prebiotics in
Pangasius production
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