Biology Reference
In-Depth Information
is still limited (Burr et al., 2005; Gatesoupe, 2005; Gatlin et al., 2007).
The capacity of non-digestible carbohydrates to support the growth of
probiotic bacteria has been proved
in vitro
(Rurangwa et al., 2009), and
in
in vivo
trials with juvenile tilapia fed on dietary yeast culture or short
chain fructo-oligosaccharides, which modifi ed the intestinal microbial
communities (Zhou et al., 2009). In fi sh larviculture, prebiotics have a
potential use in fi rst feeding and during the weaning of larvae. Mahious
et al. (2006), in assays with inulin and oligosaccharides in the weaning
of turbot (
Psetta maxima
) larvae, demonstrated a positive effect of fructo-
oligosaccharides on growth and a predominance of
Bacillus
sp. in bacterial
isolates.
Adding Benefi cial Bacteria
Probiotics
Probiotics, defi ned by FAO/WHO (2001) as “live microorganisms which,
when administered in adequate amounts, confer a health benefi t on the
host”, constitute a potential tool in the reduction of mortalities in the
rearing of aquatic organisms (Gatesoupe, 1999; Verschuere et al., 2000;
Gram and Ringø, 2005; Vine et al., 2006; Kesarcodi-Watson et al., 2008). In
rearing systems, where host and microorganisms share the same aquatic
environment, the defi nition of probiotic was broadened by Verschuere et
al. (2000) to also include the microorganisms which could exert a benefi cial
effect not colonizing the host (intestinal track, gills or skins) but being
present in the water. This broadens the concept, as microorganisms acting
on water quality or as biocontrol agents in water are also included.
The use of probiotics in aquaculture has been reviewed by Austin and
Brunt (2009), in the Volume 1 of the present edition. The different modes
of action of probiotics include: production of inhibitory compounds
(antibiotic, bacteriocins, organic acids, oxygen peroxide), competence for
limiting nutrients (siderophores), enzymatic contribution to digestibility of
feed, competence in adhesion to mucus, stimulation of immune system or
improvement of water quality. As mentioned by Austin and Brunt (2009),
there is still a lack of knowledge on the precise mode of action in most
probiotics, and in some cases the benefi cial effect requires the combination
of several mechanisms, e.g., attachment and growth in mucus can be a
previous requisite to exert antagonistic activity or immunostimulation on
the host.
Most of the published work on probiotics in larviculture is applied
research, with few evidences of the precise mode of action (Vine et al.,
2006). Moreover, many probiotic mechanisms have been studied
in vitro
,
which does not guarantee an
in vivo
effect (Gram et al., 2001).
Hatching or early developmental stages, before fi rst feeding, is an
adequate period for the use of probiotics. At these stages, bacteria
