Probiotic Applications in Temperate and Warm Water Fish Species - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 258

to adult sea bass (Sorroza et al . 2012) induced protection against V. anguillarum , reaching
a relative percentage survival (RPS) of 42.3% higher than the control group. In vitro assays
validated the effects of Vagococcus fluvialis on the sea bass immune system, showing high
values of phagocytic activity and peroxidase content in macrophages and head kidney (HK)
leukocytes after incubation with the live or inactivated probiotic cells (Romàn et al . 2012).
10.3 GILTHEAD SEA BREAM ( SPARUS AURATA L.)
The gilthead sea bream is a major fish species farmed in the Mediterranean. In 2011, Mediter-
ranean farms produced 97,000 tonnes (FAO FIGIS 2013). Greece was by far the largest pro-
ducer (accounting for 49% of production volume), followed by Turkey (15%), Spain (14%)
and Italy (6%). In addition, considerable production occurs in Croatia, Cyprus, Egypt, France,
Malta, Morocco, Portugal and Tunisia. Gilthead sea bream production also takes place in
the Red Sea, the Persian Gulf, and the Arabian Sea. Studies on the application of probi-
otics for gilthead sea bream have utilized Lactobacillus spp., Bacillus spp., a diverse range
of autochthonous bacterial strains and yeasts (Table 10.2). Such studies have shown benefits
for survival, growth, stress tolerance, immunity and disease resistance.
10.3.1 Survival, growth and stress tolerance
The administration of Lactobacillus fructivorans (AS17B), isolated from adult gilthead sea
bream gut, and Lactobacillus plantarum (906), isolated from human faeces, during sea bream
development was performed using Brachionus plicatilis and/or Artemia salina nauplii and dry
feed as vectors (Carnevali et al . 2004). The Lb. fructivorans and Lb. plantarum strains were
mixed at a proportion of 80% and 20% (w/w), respectively, and added to live food (either
rotifers or Artemia ) at a final concentration of 10 5 bacteria ml −1 . One group received a mix-
ture of both bacterial strains via rotifers from 5 to 26 dph and via Artemia salina from 27 to
47 dph. In treated groups, probiotic administration significantly reduced larvae and fry mor-
tality but did not improve the body growth or the standard length. In the same specimens
the probiotic influence on stress responsiveness was analysed; for this reason sea bream fry
(47 dph) were subjected to pH stress (from 6.3 to 8.6). After one hour exposure the cumu-
lative mortalities were recorded. The use of pH as a stressor induced a significantly higher
cumulative mortality in the control group than in both probiotic treated groups. Since dead
larvae were first observed after 30 min, cortisol levels and HSP70 gene expression were anal-
ysed before and after 25 min exposure to pH stress. Interestingly, pre-stress levels of HSP70
gene expression were significantly lower in both probiotic treated groups. Subsequently the
pH stress induced a significant increase in HSP70 gene expression in all stressed groups (Rollo
et al . 2006). The results obtained indicated that the administration of probiotics to sea bream
fry induced higher HSP70 levels, indicating a greater potentiality to respond to the harmful
conditions possibly present in fish farms. This hypothesis is supported by the fact that the lev-
els of cortisol were significantly lower in both groups under probiotic treatment. These results
suggested an improvement in tolerance to acute stress of fry fed with probiotics, by higher
repairing processes at the cellular level.
Improvement of growth rate was also observed when a mixture of B. subtilis , Bacillus
licheniformis and Bacillus pumilus was provided by rotifers and Artemia nauplii and added
to the water (group 1) or supplied exclusively via live prey (group 2) (Avella et al . 2010b).