International Journal of Aquaculture 2015, Vol.5, No. 41, 1-20
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soyabean level, phytase at 250 FTU/g showed a
significantly higher mean weight gain (Tukey, P<0.05)
and daily feed intake (Tukey, P>0.05, fig 3) compared
to 0 FTU/g, 500 FTU/g, 750 FTU/g and 1000 FTU/g
(Figure 4). FCR of 250 FTU/g was also lower (Turkey,
P<0.05) compared to other phytase diet (Figure 5).
Survival rate (Table 6) of fish showed a significant
decline in value with increasing levels of soya bean
(Duncan, P<0.05). A significant decrease in survival
rate (Table 7) was observed when phytase was
supplemented in diet based on 25% and 75% soya
bean with phytase (Duncan, P<0.05). Fish fed S3P1
showed the lowest survival of fish (73.08±10.88%)
compared to S3P0 (98.08±2.72%), S3P2 (96.15±0.00%),
S3P3 (94.23±2.72%) and S3P4 (94.23±2.72%). Fish
fed 100% soya bean supplemented with 250, 500 and
750 FTU/g phytase had significantly higher values
(P<0.05) of survival compared to control diet (S4P0).
Regardless of phytase level, survival rate improved
with inclusion of soyabean (Tukey, P>0.05) up to 75%
compared to fish meal diets (Table 6). Fig1-6 shows
effect of phytase and soyabean on growth performance of
the fish fed phytase diets. While figure 7 shows
weight gain performance (biweekly) of fish fed
phytase supplemented diets.
3.2 Effects of phytase on phytate hydrolysis
Significant interaction of the diets and phytase was
observed for phytate and oxalate concentration
(factorial, P<0.05). A significant phytate reduction
was achieved with phytase supplementation of 250
FTU/g and 1000 FTU/g compared to control with no
phytase (Tukey, P<0.05). Oxalate levels were lower
with phytase supplementation at all levels compared
to control (Tukey, P<0.05). Although, phytate content
varied significantly in experimental diets based on
soyabean without phytase from 0.52±0.01mg/g in diet
S1P0 to 0.40±0.01mg/g in S4P0 (Table 9), significant
reduction in phytate content was recorded in diets
based on 25% (25 FTU/g and 500 FTU/g), 50%
(250FTU/g-1000 FTU/g), and 100% soyabean meal
compared to basal controls (Duncan, P<0.05). Diet
S3P1 showed significant reduction in phytate
(0.34±0.04mg/g), compared with S3P0 (0.43±0.02),
S3P2 (0.51±0.02mg/g), S3P3 (0.55±0.01mg/g), and
S3P4 (0.44±0.01mg/g) (P<0.05). There is no significant
difference in phytate content of diets S2P3, S2P2,
S0P0, and S4P0 (P>0.05). The lowest phytate in
experimental diets was measured in S1P1
(0.14±0.01mg/g), while the highest was observed in
diet S1P2 (0.61±0.01mg/g). Phytate is negatively
correlated with phytase (r= -0.231, P>0.05). Oxalate
was also reduced significantly by phytase (r= -0. 328,
P<0.05) (Table 10).
Table 10 Correlation between treatment, phytase level, and antinutrients in experimental diet nased on full fat soya bean meal
supplemented with phytase
Pearson Correlation
Treatments
Phytase level
Phytate
Oxalate
Treatments
1
Phytase level
.327*
1
0.035
Phytate
-0.19
-0.231
1
0.228
0.142
Oxalate
0.223
-.328*
0.206
1
0.155
0.034
0.191
Note: *. Correlation is significant at the 0.05 level (2-tailed), **. Correlation is significant at the 0.01 level (2-tailed)
3.3 Water quality
Multivariate analysis of water quality showed
significant interaction between phytase and soyabean
for all parameters, except pH (Table 12) was observed
for fish. A significant effect of phytase in diet of the
fish was observed (Table 12) for dissolved oxygen
(ANOVA, P<0.05). Disolved oxygen improved
significantly with dietary phytase supplemention diets
compared to diets without phytase (Tukey, P<0.05).
There was little or no negative effect of phytase on
water quality (Table 11 and 12) as shown by improved
growth parameters (Table 13). Dissolved oxygen
concentration decreased significantly with soya bean
inclusion without phytase from 3.85±0.07mg/l in fish
