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bacteria has been reported to elevate lipase, protease and amylase activities in the intestine of
common carp (Yanbo and Zirong 2006). The application of live
B. subtilis
,
Lb. lactis
and
S.
cerevisiae
(at 10
8
CFU g
-1
) significantly improved Indian major carp weight gain and specific
growth rate (SGR), as a result of improved feed conversion ratio (FCR), protein efficiency
ratio, apparent digestibility of dietary dry matter and protein, and elevated intestinal protease
and lipase activities (Mohapatra
et al
. 2012a). With the exception of dry matter digestibility,
these improvements were not observed in carps fed a diet supplemented with dead
B. sub-
tilis
,
Lb. lactis
and
S. cerevisiae
cells, which indicates that the probiotics actively contributed
to the digestive process, either directly via contributions of digestive enzymes and vitamins,
and/or indirectly in that their metabolic activities induced elevations in the enzyme secretions
or activities of the host.
10.7.2 Carp immunity and disease resistance
A number of studies have provided information on the immune responses of Indian major
carp/rohu fed
B. subtilis
,
Lb. plantarum
and
Ps. aeruginosa
, catla fed
Lb. plantarum
and
B. megaterium
, common carp fed
E. faecium
, koi carp fed
B. subtilis
, and gibel carp fed
S.
cerevisiae
(Table 10.6). In addition, the resistance to pathogen challenge has also been stud-
ied in Indian major carp/rohu fed
B. subtilis
,
Lb. plantarum
and
Ps. aeruginosa
, catla fed
Lb. plantarum
and
B. megaterium
, common carp fed
E. faecium
, and koi carp fed
B. subtilis
(Table 10.6).
The dietary provision of
B. subtilis
has commonly been reported to improve the immune
response and disease resistance of carps. Improved survival of Indian major carp against
A. hydrophila
(IP challenged) has been reported and a dose response was observed (Kumar
et al
. 2006). The mean survival level increased significantly from 18.75% in the control
(no probiotic) fed carp to 68.75%, 81.25% and 87.50% in the carp fed
B. subtilis
at 0.5,
1.0 and 1.5 × 10
7
CFU g
-1
feed, respectively. In keeping with these elevated survival rates,
Kumar
et al
. (2008) reported increased proportions of peripheral granulocytes and monocytes
and neutrophil respiratory burst activity in a dose-dependent manner pre- and post-IP
A.
hydrophila
challenge. In addition, increased serum bactericidal activity against
A. hydrophila
was also demonstrated, with the improvements elevated in a dose-dependent manner. Nayak
et al
. (2007) fed Indian major carp
B. subtilis
at 10
8
CFU g
-1
for 60 days and reported
elevated peripheral leukocyte levels and serum protein in probiotic fed carp as well as elevated
antibody titres post challenge with
E. tarda
bacterin.
Improved resistance of Indian major carp to
A. hydrophila
has also been reported with the
application of dietary
Lb. plantarum
(Giri
et al
. 2013a) and
Ps. aeruginosa
(Giri
et al
. 2012).
Compared to the control group (11%), significantly higher survival rates were observed in the
fish groups fed diets containing
Ps. aeruginosa
at 10
7
CFU g
-1
(66.66%) and 10
9
CFU g
-1
(55.55%) (Giri
et al
. 2012).
Lb. plantarum
provided at 10
6
,10
8
and 10
10
CFU g
-1
signifi-
cantly improved survival against
A. hydrophila
but probiotic provision at 10
8
CFU g
-1
pro-
vided significantly better survival rates than all other treatments. Dose-dependent responses
were also apparent in the immunological responses assayed. At day 60, Indian major carp
fed all
Lb. plantarum
supplemented diets displayed elevated serum lysozyme activity, alter-
native complement activity and head kidney (HK) respiratory burst activity, and carp fed the
probiont at 10
8
CFU g
-1
displayed the highest levels. Elevated HK macrophage phagocyto-
sis activity was observed in all groups but SOD activity was only elevated in carp fed the
probiont at 10
8
CFU g
-1
(Giri
et al
. 2013a). In similar fashion, after 60 days of feeding on
Ps. aeruginosa
elevated lysozyme activity, alternative complement activity, HK phagocytosis
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