Page 6 - IJA2014v4n14

Basic HTML Version

International Journal of Aquaculture, 2014, Vol.4, No.15 89
-
95
http://ija.biopublisher.ca
90
algal bloom pollution (Baruah et al., 2004). Moreover
phytate can also integrate with cation groups of
protein, amino acids, starch and lipids in feedstuff
reducing the digestibility of these nutrients in fish,
poultry and pig. The ideal approach to maximise the
nutritive value of plant-based diet is through hydrolysis
of undigestible phytate by use of exogenous phytase
enzyme.
Phytase, chemically known as
myo
inositol (1, 2, 3, 4,
5, 6) - hexaphosphate phosphohydrolase, catalyses the
hydrolysis of phytate rendering P available for
absorption (Kumar et al., 2012). When phytase is
added to fish feed has proved to increase
bioavailability of nutrients in plant protein by
increasing phosphorus availability in grains and oil
seeds by dephosphorylation of myo – inositor
hexakisphosphate (phytate) and limited information is
available on incorporation of digestive enzyme
(phytase) in the diet of
O. niloticus.
There is need to
know what inclusion is optimal, both nutrients
utilization and mineral composition. The present study
aims to assess the effects of supplemented phytase on
the digestibility and mineral composition of
O.
niloticus
fingerlings.
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)
Control
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: Key: Mean followed by the same letter are not significantly different (P>0.05)
1.2 Apparent digestibility coefficient of Nile tilapia
fed phytase diets
Apparent digestibility coefficient for lipid was the
highest in the fishes fed diet 5, followed by the fishes
fed diet 6 and the lowest value was recorded in the
fishes fed diet 4. Similarly apparent digestibility
coefficient for gross energy followed the same trend
as for the apparent digestibility for protein (Table 2).
Table 2 Digestibility coefficient of Nile Tilapia fed phytase diets at different inclusion levels
Control
Treatment 2
Treatment 3
Treatment 4
Treatment 5
Treatment 6
ADC Protein
45.20
0.09
a
48.10
0.10
b
54.00
0.20
d
49.00
0.02
c
60.50
0.04
f
59.00
0.06
e
ADC lipid
53.40
0.01
d
50.70
0.07
c
46.00
0.01
b
45.0
0.01
a
63.70
0.05
f
60.00
0.05
e
ADC Gross energy
45.90
0.04
a
53.00
0.03
d
48.00
0.02
b
49.00
0.04
c
64.30
0.02
f
61.40
0.06
e
Note: Key: Mean followed by the same letter are not significantly different (p > 0.05) ADC= Apparent digestibility coefficient
1.3 Mineral composition of Nile tilapia fed phytase
diets
The mineral composition of the fishes after the
experiment is presented in Table 3. The fishes fed
diets that contained phytase had marginally higher
composition than the fishes fed diet without phytase.
The mineral composition of the fishes Ca, Mg, P, Fe,
Zn and Mn shows significant differences (p < 0.05)
among the treatments.
1.4 Mineral composition of the fish faeces after the
experiment
The mineral composition of the fish faeces after the
experiment was presented in Table 4. The result
showed a general increase in the value of the minerals
in the faeces of the group of the fish fed diet without
phytase compared with the values from other fishes
fed diets with phytase. The Table also showed a
downward trend in the value of the minerals with
increase in the level of phytase in the diets.