International Journal of Aquaculture, 2013, Vol.3, No.16, 85
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91
http://ija.sophiapublisher.com
86
broken down into small pieces, feed is exposed to
various enzymes which include proteases, lipases and
amylases (Caruso et al., 2009). The ability of fish to
metabolize a diet depends on the availability of
appropriate digestive enzymes, which mediate specific
degradation pathways modulating both physical and
chemical nature of foods (Phillips, 1969). The
measurement of specific activities (proteases, amylases
and lipases) may provide information about the whole
digestive capability and efficiency of fish species
under culture (Buddington et al., 1997). Several
previous studies (Smith, 1980; Reimer, 1982;
Ugolev and Kuzmina, 1994; Hidalgo et al., 1999;
Tengjaroenkul et al., 2000; Lundstedt et al., 2002)
have shown that the distribution and activity of
digestive enzymes within the gut is affected by
feeding habits. Fish usually display high versatility in
their feeding habits that is reflected in different
anatomical and functional features; both nutritional
and physiological. These characteristics allow them
the exploitation of a wide range of food resources,
thus improving their adaptation to changing
environmental conditions.
Level of digestion and its ultimate absorption into the
body warrants the feed efficiency and growth of fish
which is all dependent on presence of variety of
enzymes. Digestive processes in fish are less known
than in mammals. The data obtained so far on
enzymes in fish show that the digestive enzymes are
qualitatively similar to those observed in other
vertebrates. Several comparative studies of the
digestive enzymes in different fish species have been
reported (Hofer and Schiemer, 1981; Hofer, 1982;
Jonas et al., 1983; Kuz’mina and Kuz’mina, 1990;
Kuzmina and Smirnova, 1992) but very rare on our
locally culturable fish species. The aims of this study
were to determine the growth and activity of digestive
enzymes including protease, amylase and lipase in
different culturable herbivorous fish varieties when
fed on variable plant feed ingredients. The results
from this study will be used as a basis to develop feed
formulation from species specific feed ingredients, so
that optimal nutritional values and cost–effectiveness
can be obtained in different feed formulations.
1
Results
1.1
Growth
Catla catla
,
Cirrhinus mrigala
,
and
Labeo rohita
grew
equally but significantly higher than
Hpophthalmichthys
molitrix
when fed on rice polish. In other two
ingredients
Catla catla
displayed better growth on
soybean meal while
Cirrhinus mrigala
on cotton seed
meal. Growth in
Labeo rohita
was the second highest
to
Catla catla
when fed on soybean meal and to
Cirrhinus mrigala
when fed on cotton seed meal.
Hypothalmicthys molitrix
grew the least in all
dietary treatments.
Catla catla
,
however, showed
contradictory results, it gained maximum weight on
soybean meal, then rice polish and lowest but
equivalent to
Hypophthalmichthys molitrix
on cotton
seed meal (Table 1).
Table 1 Growth comparison of different fish species fed on different feed ingredients
Fish specis/Treatment
Rice polish
Soybean meal
Cotton seed meal
Catla catla
(
g)
0.5
± 0.015
aA
0.52
± 0.02
aA
0.41
± 0.001
bA
Cirrhinus mrigala
(
g)
0.5
± 0.1
aA
0.41
± 0.01
bB
0.5
± 0.006
aB
Labeo rohita
(
g)
0.52
± 0.001
aA
0.49
± 0.005
bC
0.47
± 0.05
cC
Hypophthalmichthys molitrix
(
g)
0.42
± 0.01
aB
0.40
± 0.005
aA
0.40
± 0.005
aA
Note: Data figures with different lower case letters across the rows and upper case letters down the columns are significantly
different from each other at P<0.01
1.2
Amylases
Amylase secretion level remained uniform when fishes
were fed on rice polish except
Hypophthalmichthys
molitrix
where level was significantly lower than its
counterparts. Though highest value was observed in
Cirrhinus mrigala
but level of significance was not as
prominent as observed in former species. Much lower
amylase concentrations were observed in
Catla catla
,
Labeo rohita
and
Hypophthalmichthys molitrix
when
fed on soybean meal and cotton seed meal (Table 2).
Cirrhinus mrigala
again topped other species in
amylase secretions when fed on cotton seed meal.