International Journal of Aquaculture 2015, Vol.5, No. 41, 1-20
15
hydrolysis (Hussain et al., 2011a) leading to improved
overall phosphorus utilization from phytate in the diet
(Table 8). In this research, improved growth in fish
fed 75% soya bean meal (full fat) with 250 FTU/g is
comparable to fish meal, which could possibly
substitute and effectively replace a fish meal based
diet of the fish. This finding was also reported by
Castro et al. (2011) who reported that soya bean at
75% inclusion could effectively replace fish meal in
the diet of Rain bow trout (
Oncorhynchus mykiss
)
without affecting growth. The higher growth
performance achieved with 250 FTU/g phytase
showed the better growth performance compared to
other diets (Table 6).
Table 14 Correlation between water quality, growth and nutrient utilization parameters
Pearson TRT Phytase DO pH Temp NH
3
Nitrate FNLWT WTG FI
FCR
Nitrate -.330* 0.017 -0.25
6
-0.268 -0.102 .473** 1
0.033 0.914 0.101 0.086 0.522 0.002
Mean
final wt
-.850*
*
-0.092 0.074 -0.257 -0.128 0.172 0.303 1
0
0.56
0.641 0.1
0.421 0.276 0.051
Mean
weight
gain
-.849*
*
-0.102 0.072 -0.264 -0.136 0.178 .328* .997** 1
0
0.52
0.652 0.092 0.389 0.259 0.034 0
DFI
-.630*
*
0.042 0.089 -0.251 0.051 -0.007 0.023 .798** .775** 1
0
0.791 0.575 0.109 0.747 0.963 0.886 0
0
FCR .480** -0.167 -0.28
5
0.274 -0.008 -0.137 -0.274 -.695** -.698*
*
-.449*
*
1
0.001 0.29
0.067 0.079 0.958 0.385 0.079 0
0
0.003
SGR -0.176 -0.102 0.191 -0.287 -0.102 -0.003 0.213 0.133 0.141 0.019 -.353*
0.266 0.518 0.225 0.066 0.521 0.986 0.176 0.399 0.372 0.905 0.022
PER -0.282 -0.168 0.226 -.320* -0.139 -0.092 0.262 0.239 0.246 0.114 -.375*
0.07 0.289 0.15 0.039 0.382 0.561 0.094 0.128 0.116 0.472 0.014
Improvement in growth performance in
Clarias
gariepinus
(Figure 2, 3 and 5) showed its capacity to
utilize plant-based diet when supplemented with
phytase compared with that of other fish like Nile
tilapia, which only showed better growth at 50% soya
bean with phytase (Goda et al., 2002). Additionally,
the increase in growth support the report of an
increased utilization of phosphorus from phytate
(Kumar et al., 2011), which is highly heat stable
(Nahashon and Kilonzo-Nthenge, 2011). The high
phytate in soya bean (Table 4) may also explain
improved growth in the fish (Selle and Ravindra,
2007). Castro et al. (2011) reported phytase at (4,000
FTU/g, Ronozyme) replaced 75% for Rainbow trout,
which showed better growth performance than diet
without phytase. In the studies of Li and Robinson
(1997) and Robinson et al. (2002), channel catfish fed
the diets containing 250 FTU/g phytase or above
consumed more feed, gained more weight, and had a
lower feed conversion ratio in comparison to fish fed
the basal diet containing no microbial phytase.
Nwanna et al. (2006) also reported an improvement in
growth of juvenile
Clarias gariepinus
fed phytase
supplemented diet based on oven dried soya bean
meal with the highest growth obtained with 8000
FTU/g Ronozyme phytase (Figure 6). Differences in
optimum phytase for growth, which has been reported
in several studies (Kumar et al., 2011; Hussain et al.,
2011a), may be due to differences in phytase sources
and diet formulation (Cao et al., 2007; Hussain et al.,
2011b). Survival rate in fish 75% soya bean
supplemented with 250 FTU/g showed a significant
decline in value compared to other phytase
supplemented diet, which may be due to the high fat
in soya bean compared with fish meal (Table 1) and
the inhibition of phosphorus by fat (Rezq et al., 2010),
