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International Journal of Aquaculture, 2014, Vol.4, No.08
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51
al
. (2005a), in
Pangasius pangasius
and Liebert and
Portz (2005), in Nile Tilapia, also observed
improvement in growth performance when fed
phytase-supplemented diet and attributed this to
increased bioavailability of protein and minerals.
The positive effect of phytase on the growth
performance of the fingerlings in the present study is
consistent with the results obtained by various authors
(Forster
et al.,
1999, Cheng and Hardy, 2002, Zongjia
et al
., 2003). However, some authors (Vielma
et al
.,
2000, Masumoto
et al
., 2001, Yan and Reigh 2002,
Sajjadi and Carter 2004, Yoo
et al
., 2005) have
reported no effect of dietary phytase on weight gain of
various fish species fed plant-based diets. This
discrepancy in their results may be associated with
differences in their diet composition and also to
different rearing conditions. Also the present study
support the report of Baruah
et al
., (2007a, 2007b)
who reported that supplementation of microbial
phytase in the diets had a positive effect on the growth
performance of
Labeo
rohita
juveniles.
Specific growth rate and condition factor reflect the
health status in fish (Ibrahem
et al.,
2010). The results
of specific growth rate revealed that treatment 5
(8,000units phytase/kg diet) (0.42
0.04g) had better
growth rate compared to the control, they were
significant differences (p < 0.05) between the
treatment and the control diet. This observation was
similar to Vielma
et al.
(2001) who reported that the
specific growth rate and feed conversion ratio were
significantly improved when trout were fed with
phytase supplemented diet at 2000 FTU/kg feed
(containing 55% of soybean meal)
Feed Conversion Ratio (FCR) is used to assess feed
utilization and absorption (conversion of feed to flesh).
FCR was best (0.89
0.01) with treatment 5 (8,000
units phytase/kg diet) and least recorded in control
(1.60
0.09), there were no significant difference (p >
0.05) among the treatments except treatment 5 that
was difference (p < 0.05) from the control. The result
revealed that diet containing 8,000 units phytase/kg
diet (treatment 5) was better utilized by
O. niloticus
fingerlings than control diets.
The result of the experiment also, showed that
treatment 5 recorded the highest value of protein
efficiency ratio and nitrogen metabolism of 0.17
0.02g and 308.86
0.01g respectively. Based on these
parameters, the best performance is treatment 5 (8,000
units phytase/kg diet) while the lowest was recorded
in the control. Feed Efficiency Ratio (FER) and
Protein Efficiency Ratio (PER) are used as quality
indicators for fish diet and amino acid balance. So,
these parameters are used to assess protein utilization
and turnover. These results are also in agreement with
those obtained by Baruah
et al
. (2007) who recorded
increase in FCR and PER of
Labeo rohita
fingerlings
fed experimental diets containing various levels of
microbial phytase for 60 days compared to the control
which had the least value.
Apparent net protein utilization recorded during the
experiment was highest in treatment 5 (8,000 units
phytase/kg diet) and there were significant differences
(p < 0.05) among the treatments. This results support
the report of Debnath
et al
. (2005b) who reported that
phytase supplemented diet in pangus increased
apparent net protein utilisation.
The water quality parameters; temperature, dissolved
oxygen and pH were measured during the experiment.
The values obtained for the parameters were within
the recommended range for warm water fishes (Boyd,
1981). From the result obtained phytase could be used
in aquaculture as they did not alter the water quality.
3 Conclusion
Capture fisheries have failed to meet the demand of
Nigeria populace and to bridge this gap aquaculture as
been giving priority. There is a need to enhance
awareness among fish nutritionists and the fish feed
manufacturing industry on the use of phytase as an
effective and efficient approach in the formulation of
cost effective, growth promoting and low polluting
fish feeds based on plant protein sources, for
profitable and sustainable aquaculture production.
Therefore considering the result of the experiment, I
strongly recommended phytase at 8,000 units phytase/kg
diet for fish farmers who want to embark on
large-scale fish production.
4 Material and Methods
4.1 Experimental system
The experiment was carried out using twelve glass
tanks (60 ×30×30 cm) for 8 weeks in the Department
of Fisheries and Aquaculture Technology Laboratory
of the Federal University of Technology, Akure,