Agriculture Reference
In-Depth Information
In the first study on this topic, Ghosh and co-workers (2007) demonstrated that probiotic
Bacillus subtilis
, isolated from the intestine of mrigal carp (
Cirrhinus mrigala
Hamilton),
improved the reproductive performance of four species of livebearing ornamental fish: guppy,
Mexican molly, green swordtail and southern platyfish. The probiont was administered for one
year by incorporation in fish feed at four different concentrations (5 × 10
5
cells g
-1
,5× 10
6
cells g
-1
,5× 10
7
cells g
-1
and 5 × 10
8
cells g
-1
). The results showed that probiotic sup-
plementation significantly improved the gonadosomatic index (GSI: a well-used indicator of
ovary development and fecundity) and the fecundity of spawning females in all fish species.
In addition, Ghosh and co-workers (2007) observed that both the length and the weight of fry
were significantly enhanced by probiotic treatment in all four species. Moreover, the number
of dead and deformed fry was reduced in fish fed the probiotic. By analysing the results on
the basis of the concentration of probiotics supplemented to the diet, improvements were not
dose dependent, with the use of the higher concentration not always leading to significantly
improved reproductive performance of the spawners.
In a more recent study, Abasali and Mohamad (2011) evaluated the effects of dietary incor-
poration of a commercial probiotic mixture, composed of equal portions of
Lactobacillus
acidopholus
,
Lactobacillus casei
,
Enterococcus faecium
and
Bifidobacterium thermophilum
(Primalac: Nikandisham Farjad Commerce Corporation, Tehran, Iran), on southern platyfish.
After 26 weeks treatment with the probiotic at three different concentrations (0.04%, 0.09%
and 0.14% of feed), females showed improved GSI and fecundity. In addition, larvae from
treated females showed higher length and elevated survival rate compared to larvae derived
from control females. However, weight and deformation rate were not affected by probiotic
treatment.
12.5.2 The effect of probiotics on zebrafish reproduction
Due to a number of favourable characteristics, such as its fully sequenced genome, ease of
culture, small size and translucent larval stages, the zebrafish is considered an excellent verte-
brate model system for studying reproductive genetics and development (Penberthy
etal.
2002;
Keller
et al.
2006; Shiels
et al.
2009). Several studies have utilized this model to assess the
effect of a commercial
Lactobacillus rhamnosus
probiotic (Synbiotec Srl, Italy) on reproduc-
tion. The wide range of results obtained at the molecular, macromolecular and physiological
levels provides a strong level of understanding, even if still incomplete, of the possible mech-
anisms through which probiotics can stimulate reproductive performances.
Gioacchini
etal.
(2010a; 2011) reported that after feeding zebrafish experimental diets con-
taining
Lb. rhamnosus
(at 10
6
CFU g
-1
) for 10 days, the daily numbers of ovulated eggs rose
significantly compared to control levels, starting from the second day of administration. In par-
ticular, probiotic treated females reached the maximum daily ovulated egg production levels on
day 4 (a twofold increase with respect to control levels), with egg production remaining high
during the following days (Gioacchini
et al.
2010a; 2011). It was also demonstrated that the
embryos produced by zebrafish females fed with the
Lb. rhamnosus
IMC 501
®
showed higher
hatching rate and faster embryonic development, characterized by the fact that embryo hatch-
ing was brought forward by 4 h compared to the control group (Gioacchini
et al.
2010a). In
probiotic treated females, both real-time PCR and culture based methods revealed alterations
in GI tract microbiota, characterized in the gut by high levels of
Lb. rhamnosus
, which was
absent in the control females (Gioacchini
et al.
2011). At the same time, PCR-DGGE analysis
revealed that the probiotic was able not only to populate the GI tract but also to modulate the
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