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International Journal of Aquaculture, 2014, Vol.4, No.08
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50
Table 3 Growth performance and nutrient utilization of Nile tilapia fed phytase diet
Treatment 1
Treatment 2
Treatment 3
Treatment 4
Treatment 5
Treatment 6
Initial mean weight
6.19±0.02
a
6.23±0.04
a
6.18±0.01
a
6.25±0.04
a
6.27±0.01
a
6.23±0.04
a
Final mean weight
9.11±0.01
a
9.22±0.02
b
9.53±0.00
c
9.26±0.02
b
11.59±0.06
e
9.87±0.20
d
Mean weight gain
2.92±0.01
a
2.99±0.08
b
3.35±0.06
c
3.01±0.01
b
5.32±0.67
e
3.64±0.24
d
Weight gain (%)
47.05
2.04
a
48.0
1.00
b
54.15
0.45d 48.25
0.75
c
84.95
10.95
f
58.45
1.25
e
Specific growth rate
0.27
0.01
a
0.27
0.04
a
0.30
0.03
a
0.27
0.03
a
0.42
0.04
b
0.33
0.01
a
Feed conversion ratio
1.60
0.09
b
1.56
0.03
b
1.40
0.19
b
1.56
0.01
b
0.89
0.01
a
1.28
0.09
ab
Protein efficiency ratio
0.09
0.00
a
0.10
0.01
a
0.11
0.00
a
0.10
0.01
a
0.17
0.02
b
0.12
0.01
a
Protein productive value
24.51
0.01
f
7.99
0.01
a
23.70
0.00
e
19.37
0.01
c
15.81
0.03
b
21.22
0.01
d
Nitrogen metabolism
264.59
0.02
a
267.18
0.03
b
271.68
0.02
d
268.22
0.00
c
308.86
0.01
f
278.43
0.06
e
Gross feed conversion efficiency 62.50
0.01
a
64.10
0.01
b
71.43
0.02
c
64.10
0.02
b
112.36
0.00
e
78.13
0.03
d
Apparent net protein utilization 24.52
0.00
e
8.27
0.01
a
23.99
0.02
d
19.65
0.03
b
25.65
0.01
f
21.51
0.00
c
Note: Mean followed by the same letter are not significantly different (p > 0.05)
Table 4 Mean Weekly Water Parameters
Parameters
0
1
2
3
4
5
6
7
8
9
Mean
Temperature (
℃
)
24.00 25.00 26.00 26.02 26.03 26.00 25.00 25.40 25.30 25.40 25.42
0.63
Dissolved oxygen (mg/L) 6.40 6.50 6.50 6.60 6.60 6.40 5.90 6.30 6.40 6.70 6.43
0.21
pH
6.90 6.80 6.90 6.90 7.20 7.10 7.10 7.50 7.20 7.40 7.10
0.22
1.4Water quality parameters of experimental tanks
The water quality parameters of the experimental
tanks, temperature, dissolved oxygen and pH were
closely related. The values varied from 24.00 to 26.03
℃
,
5.9 to 6.7mg/L and 6.8 to 7.5 respectively (Table 4).
2 Discussion
In this study, experimental diets were formulated with
different levels of phytase for
O. niloticus
fingerlings.
The proximate composition of the experimental diets
of this study supports the growth of
O. niloticus
finger-
lings and this corroborate the report of Eyo (1995)
that for growth at maximum rate, fry, fingerlings and
juveniles must have a diet in which nearly half of the
digestible ingredients consist of balanced protein.The
proximate composition of
O. niloticus
fingerlings
before and after experiments fed on experimental diets
is presented in Table 3. The results indicate that the
diets supported the growth of fish as increased body
protein levels were recorded in all the treatments. This
also showed that the protein requirement for the
O.
niloticus
fingerlings was met for body maintenance
and growth. The reason for this might be as a result of
presence of phytase supplementation enhances
digestibility of minerals which are bound to phytate.
The higher body protein deposition and increased
weight gain is indicative of the adequacy of the
protein content and higher protein intake.
Results from the present study demonstrated that
incorporation of phytase in toasted and incubated
soybean meal diets improved overall growth
performance in
O. niloticus
. The results of the study
showed that fishes fed diets with phytase had higher
mean weight gain, specific growth rate, protein
efficiency ratio, feed conversion ratio, gross feed
conversion efficiency and nitrogen metabolism than
the group of fish fed diet without phytase. The
enhancement of the growth performance in the fishes
feed that contained phytase increased with the
increased in the levels of phytase addition. This
improvement could be attributed to the liberation of
more phytate phosphorus (P) from the diets by the
phytase enzymes, which the fishes utilized for the
better performance. The higher performance could
also be ascribed to higher dietary nutrients
bioavailability and digestibility made possible by the
phytase enzymes.
The results of this present study was similar to the
report of Jackson
et al
. (1996) who reported an
increase in weight gain in channel catfish fed
phytase-supplemented diets containing only plant
protein sources. Also, similar performance of rainbow
trout (Vielma
et al
., 1998, 2002) and stripped bass
(Papatryphon
et al
., 1999) was also reported and
attributed solely to improved use of P from the phytate.
Vielma
et al
. (2004), in rainbow trout and Debnath
et