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higher dose (10
6
CFU ml
-1
for 5 min) on sterilized eggs prior to hatch. Despite the frequency
of the treatment, no benefits in survival rate were observed, along with similar bacterial load
compared to the control. This could be due to the rather low dose applied in the first part
of the treatment. However, addition of the probiotic mixture via live feed (10
6
CFU ml
-1
for 30 min on days 0, 1, 17 and 18) was conducted in two other trials, resulting in higher
survival in treated larvae (60 days post-feeding) and enhanced growth in one of the two trials.
Therefore, live feed was shown to be an appropriate vector for probiotic transmission to
halibut larvae (Bjornsdottir
et al
. 2010).
9.4.2 Turbot (
Scophthalmus maximus/Psetta maxima
)
Turbot is a valuable commercial species for aquaculture production and although commercial-
scale production faces many challenges production output has rapidly increased over the last
decade, reaching 75,000 tonnes in 2011 (FAO FIGIS 2013). Increasing commercial interest
in turbot production has also resulted in an increasing effort to study the gut microbiota and
methods for microbial fortification. Probiotic applications of
Lb. plantarum
/
Carnobacterium
sp. (Gatesoupe 1994),
Vibriopelagius
(Ringø 1999),
C.divergens
(Ringø 1999),
Lc.lactis
(Vil-
lamil
et al
. 2002),
Phaeobacter
strain 27-4 (Planas
et al
. 2006; formerly
Roseobacter
sp. 27-4)
and
P. acidilactici
(Villamil
et al.
2010) have been reported, predominantly, in larviculture via
rearing water or live feed (Table 9.4).
Colonization success of probiotic strains can be influenced by the application method (rear-
ing stage, administration vector, dose and frequency of treatment) and host specificity. It has
been reported that the addition of probiotics early post hatch in turbot larviculture led to a
greater colonization success than when applied a few days later (Ringø and Vadstein 1998)
and an autochthonous probiotic strain (
V. pelagius
) was shown to colonize the turbot larval gut
better than an allochthonous strain (
C. divergens
) (Ringø 1999). Further, the work of Makridis
et al
. (2000) demonstrated that a strain originating from turbot larvae colonized turbot larvae
better than a strain isolated from an adult. The authors also compared the addition of probi-
otics via rearing water and/or rotifers' supplementation. They reported a similar effect of the
treatments, as discharging rotifers to the tanks influenced the water microbiota similarly with
respect to the probiotics added to the rearing water.
The benefit of a probiotic treatment through bathing of ova, and resulting larvae, has been
evaluated in turbot (Hjelm
et al
. 2004). An allochthonous strain,
Phaeobacter
sp., enhanced
larval survival when applied at a dose of 10
7
CFU ml
-1
prior to hatch. The dose required for
improved disease resistance by an autochthonous
Vibrio
strain transmitted via enriched rotifer
to larvae challenged with
V. splendidus
ranged from 10
6
to 5 × 10
7
CFU ml
-1
(Gatesoupe
1997). Several other allochthonous strains, mainly LAB and
Bacillus
spp., have been beneficial
in turbot larviculture when supplemented (10
3-7
CFU ml
-1
) via live feed (Gatesoupe 1991;
1993; Daga
et al.
2013) and even when challenged by pathogenic
Vibrio
strains (Gatesoupe
1994; Planas
etal.
2006). Nevertheless, probiotic supplementation may lead to unclear benefits
under normal rearing conditions (Gatesoupe 1994; Ringø and Vadstein 1998; Ringø 1999;
Makridis
et al.
2000; Villamil
et al
. 2010).
Rearing water treated with
V. pelagius
(10
5
bacteria ml
-1
), an autochthonous strain of tur-
bot, also influenced the gut microbiota of turbot larvae (Ringø
et al
. 1996). Moreover, better
larval uptake of the probiotic
P. acidilactici
was achieved via rearing water compared to rotifer
supplementation (Villamil
et al.
2010). Nevertheless, encapsulation of an allochthonous mix-
ture of
Lactobacillus
and
Pediococcus
spp. in
Artemia
(∼10
6
CFU ml
-1
per day) fed to larvae
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