International Journal of Aquaculture, 2016, Vol.6, No.2, 1
-
9
6
Figure 5 Histology of stomach (*), liver (+) and intestine (#) of control
Note: (a) compared with animals treated with 6x107 CFU L1 of each strain of ENT suspension at stages E; (b), L (c) and E&L (d)
and treated with 6x104 CFU L-1 of each strain of LAB suspension at stages E; (e), L (f) and E&L (g). Bars= 50 µm
4 Discussion
The use of probiotics in aquaculture has increased exponentially in the last years (Verschuere et al., 2000; Reid et
al., 2003; Romalde et al., 2005). However, commercial probiotics in fish culture are relatively ineffective. Most
products include non-autochthonous strains unable to survive or remain viable in the intestinal environment
(Ridha and Azad, 2015). Different authors have shown from long time ago (Kotarsky and Savage, 1979, Marteau,
2011) and demonstrated lately by the application of molecular biology techniques, the specie-specificity of the
microbioma, or autochtonous microbiota, and also related to each specific tract of mucosa (Chi et al., 2014). It is
essential the isolation and study of putative native probiotic microorganisms that are part of the microbiome of
each specific host. Such strains have higher possibilities to survive and remain because they have already resisted
these environmental conditions (Ghosh et al., 2007). Based on previous
in vitro
evaluations, our research group
has selected five autochthonous lactic acid bacteria (three
E. faecium
and one
P. acidilactici
strains) as novel putative
probiotics (Guidoli et al., 2015). However, the definitive application and clinical evidence of their beneficial effects
should be evaluated through
in vivo
assays (ISAPP, 2011). Therefore, in this work we evaluated the effect of the
administration of two different formulae composed by beneficial autochthonous microorganisms isolated on two
seasons on the survival, mean weight, biomass and histological parameters of
P. mesopotamicus
larvae.
There are three critical items related to probiotic application: the stage of the biological cycle, the optimal dose
and the way in which they should be administered to the host. Pasteris et al. (2012) suggested that the colonization
of the skin (or scams) and the gastrointestinal tract of fishes occurs together with the ontogeny, as a way to be
incorporated into the microbioma of each specie. The microbial adhesion to the eggs’ surface is, then, the main
factor to determine the development of the epibiota. Afterwards, the ingestion of microorganisms in larval stages
results in the establishment of a dominant intestinal microbiota that seems to persist during the fish life.
Unfortunately, there is no general consensus on the other two critical items cited before. Bibliographic references
suggest doses of administration from 1x10
3
to 1x10
9
CFU and different ways of administration such as balanced
food or environmental water (Brunt and Austin, 2005; Bagheri et al., 2008). The last critical item is the way of
administration, being widely used the food (Brunt and Austin, 2005; Bagheri et al., 2008). In this work, the
selected beneficial microorganisms were added at different doses, stages and systems of administration.
Although ANOVA analysis did not show significant differences or interactions of different treatments with ENT
suspension and control, the trend analysis of the dose effect showed significant differences for the mean weight
and biomass. This test showed the quadratic contrast as the best model to describe the polynomial function for
both variables, indicating the dose 7 (6x10
7
CFU L-1 of each strain) as the most effective one. The better effect of
