Agriculture Reference
In-Depth Information
9.2.2 Brown/sea trout (
Salmo trutta
)
According to the Food and Agriculture Organization (FAO), the main producers (
100
tonnes/year) of brown/sea trout in seawater or freshwater in 2010 were the Russian Federation
(accounting for 80% of the global total, almost exclusively in freshwater), Italy, Roma-
nia, France, the UK, Germany, Denmark and Bosnia and Herzegovina (FAO FIGIS 2013).
Moreover, it is well known that native species of brown/sea trout are important in terms of
their contribution to recreational fisheries and angling (Merrifield
et al
. 2010a).
In contrast to rainbow trout, few probiotic studies have been conducted on brown trout
(Table 9.1). Balcázar
et al
. (2007a) observed a correlation between colonization with probi-
otic strains (
Lc. lactis
subsp.
lactis
or
Leu
.
mesenteroides
) and non-specific humoral responses
such as alternative complement pathway activity and lysozyme activity. Further studies demon-
strated that administration of these probiotic strains enhanced the phagocytic activity of the
HK leukocytes and conferred protection against furunculosis in brown trout (Balcázar
et al
.
2009). Further, some probiotic organisms may help to reduce brown trout fungal infections
(Carbajal-González
et al
. 2013). The capacity of potential probionts to adhere to brown trout
skin mucus and to reduce the adhesion of
Saprolegniaparasitica
cysts under exclusion, compe-
tition and displacement conditions were analysed
in vitro
by Carbajal-González
et al
. (2013).
Almost all of the tested bacterial isolates reduced fungal cyst adhesion ratios significantly; the
bacterial isolates which most effectively reduced the adhesion of the pathogen were identified
as belonging to the species
A. sobria
and
Pseudomonas fluorescens.
.
>
9.2.3 Atlantic salmon (
Salmo salar
L.)
Compared to the depth of information available on probiotic applications in rainbow trout,
considerably less information is available for Atlantic salmon. The available information, sum-
marized in Tables 9.1 and 9.2, can be divided into
in vivo
studies (Smith and Davey 1993;
Austin
et al
. 1995; Gildberg
et al
. 1995; Robertson
et al
. 2000; Gram
et al
. 2001) and
ex vivo
studies (Ringø
et al
. 2007a; Salinas
et al
. 2008; Kristiansen
et al
. 2011).
To our knowledge, the first study on probiotics in Atlantic salmon was carried out by Smith
and Davey (1993). The authors isolated 100 bacteria from brown trout and tested their ability
to inhibit the
in vitro
growth of
A
.
salmonicida
and suggested that the observed inhibition was
caused by competition of free iron. The most promising isolate, a fluorescent pseudomonad,
Ps
.
fluorescens
F19/3, was further tested to compete against
A
.
salmonicida
in asymptomat-
ically infected pre-smolt Atlantic salmon. The results from the four experiments revealed a
significant reduction in the frequency of stress-induced furunculosis after a bath treatment.
Based on their results, the authors suggested that
Ps
.
fluorescens
F19/3 excluded
A
.
salmoni-
cida
on the external surfaces. In contrast, Gram
et al
. (2001) reported that
Ps. fluorescens
(strain AH2) was not effective at reducing Atlantic salmon mortalities when challenged by
cohabitation with
A
.
salmonicida
infected fish. However, the strain showed strong
in vitro
inhibitory activity towards
A
.
salmonicida
. Based on their results, the authors concluded that
a strong
in vitro
growth inhibition alone cannot be used to predict possible
in vivo
effects and
suggested that the lack of effect in the
in vivo
experiment might be due to the infection route
of the pathogen or that the level of the probiont may not have been sufficient to outcompete
the pathogen.
Austin
et al
. (1995) used a potential probiont,
Vibrio alginolyticus
, obtained from a com-
mercial shrimp hatchery in Ecuador, in an Atlantic salmon pathogen challenge. Salmon were
Search WWH ::
Custom Search