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International Journal of Aquaculture, 2014, Vol.4, No.08
http://ija.sophiapublisher.com
49
the world for its excellent biological characteristics.
However, there are a large number of feed additives
available to improve fish growth performance,
enzyme (phytase) are feed additives can be used as a
growth promoter but the mechanism of action of
phytase as a growth promoter is yet to be adequately
researched. It was considered that phytase could have
the ability to increase bioavailability of nutrients in
plant protein. This study was conducted to assess the
performance of
O. niloticus
fingerlings fed diets
containing differently processed soybean meals
supplemented with phytase
1 Results
1.1 Proximate composition of the experimental diet
The crude protein of the diets was similar and ranged
between 30.8 and 31.5%. The values of the ether
extract, ash content, crude fibre and nitrogen free
extract were similar and ranged between 16.31 and
16.96%, 8.1 and 8.3%, 10.9 and 12.05 and 31.69 and
33.79% respectively (Table 1).
Table 1 Proximate composition of the experimental diet (DM)
Diet 1
Diet 2
Diets 3
Diet 4
Diet 5
Diet 6
Crude Protein
31.0±0.02
a
31.30±0.04
a
30.80±0.08
a
31.50±0.10
a
31.00±0.02
a
31.10±0.10
a
Ash
8.10±0.05
a
8.50±0.06
a
8.00±0.07
a
8.30±0.08
a
8.30±0.08
a
8.30±0.01
a
Ether extract
16.69±1.02
a
16.31±0.07
a
16.95±0.75
a
16.29±0.80
a
16.96±0.86
a
16.33±0.67
a
Crude Fibre
10.9±0.92
a
11.10±0.75
a
11.50±0.08
a
11.88±0.02
a
12.05±0.10
a
12.05±0.95
a
NFE
33.30±0.01
a
34.79±0.10
a
32.69±0.10
a
32.02±0.98
a
31.69±0.89
a
32.22±0.10
a
Note: Mean followed by the same letter are not significantly different (p > 0.05). NFE = Nitrogen free extract, DM = Dry matter
1.2 Proximate composition of the fish before and
after the experiment
The result of the proximate composition of the initial
and final body composition of tilapia fingerlings fed
on the experimental diets is presented in Table 2. The
fish fed diet 5 had the highest numerical value of
crude protein while the least value was obtained from
fishes fed diet 2. The highest ash content value was
obtained from fishes fed diet 1, 2, 3 and 6 while the
lowest value was obtained from fished fed diet 4
and 5.The fat content composition was highest in
fishes fed diet 6 while the least composition
recorded in fishes fed diet 1. The highest crude fibre
(%) was obtained from fishes fed diet 1, 3 and 6
while the lowest value was obtained from fished fed
diet 2 and 5. Fishes fed diet 6 had the lowest value
of Nitrogen Free Extract (NFE), while those fed diet
2 had the highest.
Table 2 Proximate composition of fish before and after the experiment
Before
Treatment 1
Treatment 2
Treatment 3
Treatment 4
Treatment 5
Treatment 6
Crude Protein 55.80±0.02
a
63.40
0.05
e
58.39
0.07
b
63.19
0.04
d
61.99
0.25
g
63.75
1.0
f
62.49
0.45
c
Ash
17.50±0.05
a
20.01
1.75
c
19.90
0.05
c
20.20
0.05
c
19.20
0.05
b
19.20
0.15
b
20.20
0.02
c
Ether extract 3.50±0.06
a
7.40
0.01
b
7.70
0.00
c
7.80
0.15
d
8.41
0.31
f
8.10
0.05
e
9.70
0.71
g
Crude Fibre
1.90±0.01
a
2.19
0.05
d
1.98
0.02
b
2.21
0.15
d
2.12
0.06
c
2.04
0.05
b
2.22
0.08
d
NFE
21.30±0.60
g
7.00
0.05
d
12.03
0.01
f
6.60
0.09
b
8.28
0.08
e
6.91
0.07
c
5.39
0.17
a
Note: Mean followed by the same letter are not significantly different (p > 0.05). NFE = Nitrogen free extract
1.3 Growth and nutrient utilization of Nile Tilapia
fed phytase diets
The growth response of Nile tilapia fingerlings fed
on diet containing varying levels of phytase is
shown in Table 3. The highest value of mean weight
gain was obtained from fish fed diet 5, followed by
the fish fed diet 6 while the lowest value was
obtained from fish fed diet without phytase (control
diet). There were significant differences in the mean
weight gain of the fish among the treatments.
The specific growth rate of fish fed diet 5 was
significantly (p < 0.05) higher than the specific growth
rate of fishes fed other diets, while the specific growth
rate of fishes fed diets 1, 2, 3, 4 and 6 were similar
(p > 0.05). The value of the feed conversion ratio
followed the same trend while protein productive
value, nitrogen metabolism, gross feed conversion
efficiency and apparent net protein utilization were
significantly (p < 0.05) among the treatments.