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body weight of the fish. Thus, the amount of daily
feed ration (DFR) at each sampling time was
calculated using the mean body weight (MBW) and
the total number of the fish (N) and the feeding rate
per day (FR/d) using the following formula:
DFR=(MBW×N×FR)/d
(Nandlal and Pickering,
2004).
4.3 Data collection
During the experiment, dissolved oxygen concentration
and pH were measured daily using Hydrolab, Model
“Multi 340I/SET. To evaluate the growth performance
and feed utilization efficiency of juvenile
Oreochromis
niloticus,
all the fish were measured for their weight
and length at two weeks intervals. Mortality of the
fish was also registering throughout the experiment.
4.4 Data analysis
Based on the data collected during the experiment,
growth performance parameters such as final mean
body weight (FMBW), mean body weight gain
(MBWG), specific growth rate (SGR, %/day),
metabolic growth rate (MGR, gkg
0.8
/day), feed
conversion ratio (FCR), protein efficiency ratio (PER)
and survival rate (SR) were calculated as described by
Hardy (2002) and Ridha (2006). These values were
calculated as:
MBWG = FMB
W－
IMBW;
SGR in %/day = [(lnFMBW)
－
lnIMBW)/dt] ×100;
MGR, gkg
0.8
/day = (MBWG)/ [{(IMBW/1000)
0.8
+
(FMBW/1 000)
0.8
}/2]/dt;
FCR = FI (g)/ Wg (g);
PER = BWG (g)/ CPF (g); and
SR = [(NSF
－
NDF)/NSF]×100
Where dt is number of trial days, FI is feed intake,
CPF is crude protein feeds, NSF is Number of stocked
fish and NDF is number of dead fish.
4.5 Statistical Analysis
Mean growth performance parameters, feed
conversion ratio and survival rate were analyzed using
analysis of variance (ANOVA). T-test and Turkey test
were used to identify the mean value differences for
the analysis of variance. Statistical significance was
determined at p<0.05. All calculation was performed
using SPSS 14 versions of statistical software.
Acknowledgement
We would like to express our appreciation to all staffs of the Biology
department who collaborated in different ways while we were conducting
our research. We would also indebted to the NORAD project and Hawassa
University for their genius assistant to provide fund and other facilities for
the research.
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