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these results were associated with an improved resistance to a
Vibrio
infection. Whether this
effect on the immune response of shrimp was also implicated in the improved tolerance of
the probiotic fed post larvae to salinity change (freshwater and 60% salt water) and nitrite
stress (up to 300 mg l
-1
of nitrite N) was however not investigated. Other authors also reported
modulation of the immune response in juvenile white shrimp fed a
V. alginolyticus
probiotic
during larviculture stages under a WSSV challenge but no clear correlation between immune
parameters and viral resistance was apparent (Rodriguez
et al.
2007).
Beyond the resistance to vibriosis, some studies have also investigated the effect of probi-
otics on other parameters such as larval development or susceptibility to stress. For instance,
Liu
et al.
(2011b) recently evaluated the effect of a specific
B. subtilis
strain (E20), isolated
from human food, on the development, tolerance to environmental stress and immune response
of white shrimp larvae. Interestingly, the results showed that
B. subtilis
E20, administered in
the water culture at a high concentration (10
6
CFU ml
-1
), was able not only to improve larval
survival but also to accelerate development. This probiotic effect on larval development was
also reported in other shrimp species such as
M.rosenbergii
larvae, for which
B.subtilis
treated
Artemia
nauplii accelerated the rate of metamorphosis (Keyzami
et al.
2007). This effect has
often been attributed to an ability of the probiotic strain to improve the nutritional status of
shrimps through an increase in digestive enzyme activities such as proteases (Ziaei-Nejad
etal.
2006; Liu
et al.
2009; Zhou
et al.
2009).
Based on these findings and the development of empirical approaches, probiotic application
in larval production has quickly emerged in the main shrimp producing countries and is now
a commonly applied alternative to antibiotics. Decamp
et al.
(2008) reviewed field data con-
cerning the use of a commercial probiotic preparation containing mixed
Bacillus
spp. strains,
based on data from Thai and Brazilian hatcheries, with
P. monodon
and
L. vannamei
respec-
tively. The authors report that when directly administered in the larval tank at 1-5 × 10
4
CFU
ml
-1
,the
Bacillus
strains, which were selected from over 70 strains of
Bacillus
according to
their
in vitro
antagonism towards pathogenic
Vibrio
species, yielded a similar performance as
prophylactic antibiotic treatments.
11.4.1.2 Vector of administration and administration cycle
In crustacean larvae and early post larvae, the main way to deliver microbial products is through
direct application into the water (Table 11.1). In this case, based on the data available today
and on unpublished data (Chim, personal communication), the optimal dosage of probiotics
used in crustacean larviculture seems to be between 10
4
and 10
6
CFU ml
-1
.
However, other vectors of administration via inert or live feeds have also been investigated.
Artemia
nauplii are widely used in marine crustacean hatcheries around the world.
Artemia
like
other live feed can be a source of pathogenic bacteria in hatchery environments (Avila-Villa
et al.
2011;
Chapter 16
) and probiotics have been proposed as a solution to reduce the risks of
contamination (Meunpol
etal.
2003; Vershuere
etal.
2000a). Changes in bacterial assemblages
as well as protection against pathogens have often been measured when probiotics are applied
to live feeds including
Artemia
and rotifers (Verschuere
et al.
1999; Marques
et al.
2006a;
Rojas-Garcia
et al.
2008; Qi
et al.
2008; Pintado
et al.
2010).
Artemia
have also been proposed as an efficient way to deliver nutrients, antimicrobial
agents, vaccines, or probiotics to fish and crustacean larvae. Several studies have been con-
ducted to assess probiotic encapsulated
A. franciscana
nauplii in shrimp larvae and post larvae
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