Agriculture Reference
In-Depth Information
V. anguillarum
(10
6
CFU ml
-1
) to a level beneath the uninfected controls. In a similar study
(D'Alvise
etal.
2013), this
Phaeobacter
strain along with two others were shown to reduce cod
larval mortality, but the extent of this effect was influenced by the time of introduction of the
probiotic with respect to the pathogen (48 h before, simultaneously or 48 h after). Since earlier
addition of probiotics proved to be most efficient, use of
Phaeobacter
spp. as a prophylactic
treatment against bacterial infections may be the most promising application for larviculture.
The capability of TDA production by the different
Phaeobacter
strains was correlated with
their probiotic impact, suggesting that TDA production is among the key mechanisms of their
probiotic action. Finally, Lazado
et al
. (2012) demonstrated that two bacterial strains (
Psy-
chrobacter
sp. and
Pseudomonas
sp.) isolated from cod GI tract could be orally delivered by
feed (10
6
CFU g
-1
) to juveniles and could improve their digestive capacity after 40 days of
feeding, but not 20 days. Few studies have evaluated the cod immunomodulative properties
of probiotics, but the potential of autochthonous cod strains was confirmed by
in vitro
stud-
ies (Caipang
et al
. 2010; Lazado
et al
. 2010), the latter study emphasizing the importance of
probiotic viability for enhanced response.
In summary, probiotic applications in cod larviculture have been mainly administered via
rearing water (10
5-7
CFU ml
-1
) and proved to be beneficial by enhancing survival, develop-
ment, vitality and microbiota control as well as disease resistance. Most probiotics evaluated
were allochthonous strains. The study of D'Alvise
etal
. (2012) demonstrated that
Phaeobacter
gallaeciensis
can reduce
V. anguillarum
in axenic live feed cultures, which could be another
probiotic administration vector to larvae. Juvenile probiotic treatments have been achieved by
dry feed supplementation (10
6-9
CFU g
-1
), generally using autochthonous strains. Few stud-
ies have considered the use of multispecies probiotics, while a minimal beneficial treatment
appears to be 4-6 weeks of daily feeding. LAB colonization, microbiota control and enhanced
enzymatic activity, growth, survival and disease resistance were the main effects observed.
Overall, the findings indicate a broad activity spectrum for probiotics, benefiting multiple or
all rearing stages.
9.3.2 Atlantic pollack (
Pollachius pollachius
)
High demand for fresh fillets of white fish has stimulated the development of other farmed
gadoid species. Pollack aquaculture was initiated almost two decades ago in France and Spain.
As for cod, its sensitivity to pathogens and low survival at early phases of rearing has delayed
culture developments. Further, its slow growth compared to Mediterranean fish species is
another major weakness. Nevertheless, some information on probiotics is available. Gatesoupe
(2002) investigated the effects of two commercial probiotic strains supplemented to
Artemia
nauplii and then fed to pollack larvae. The products contained
P. acidilactici
and
S. cerevisiae
.
This study was the first attempt to evaluate the synergistic effect of LAB and yeast. Formalde-
hyde was used to disinfect
Artemia
cysts and nauplii, combat the dominating Gram-negative
bacteria and reduce the high bacterial load inherent to
Artemia
culture, while the probiotics
were introduced in the enrichment process. In this study, live feed was shown to be an appro-
priate vector for probiotic transmission to larvae and the probiotics applied enhanced larval
growth, especially when applied together. However, the disinfection method used affected
P.
acidilactici
and after three months led to the emergence of a resistant microbiota. It was con-
cluded that
P. acidilactici
was a promising probiotic for fish larvae, while a careful application
of
S. cerevisiae
may be valuable if bacterial imbalance can be avoided.
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