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*Corresponding author:
Email: kassayebalkew@gmail.com, +251 936211992 https://dx.doi.org/10.4314/eajbcs.v4i2.3S

Oreochromis niloticus

Belete Berhanu1, Kassaye BalkewWorkagegn1, 2*, Natarajan Pavanasam1

1Department of Aquatic Sciences, Fisheries and Aquaculture, College of Natural and Computational
Sciences, Hawassa University, P. O. BOX: 05, Hawassa, Ethiopia

2Centre for Aquaculture Research and Education (CARE), College of Natural and Computational
Sciences, Hawassa University, P. O. BOX: 05, Hawassa, Ethiopia

KEYWORDS:

Sex-reversal;

Methyl testosterone;

Mono-sex production;

Hapa;

Nile tilapia

ABSTRACT

The present study aimed at developing all-male Nile tilapia using 17α-methyl testosterone
(17α-MT) along with its growth and feed utilization performances. Three days old Nile
tilapia fry were stocked in plastic jars with 5 L capacity installed in four fiber glass tanks.
The fry were fed with 0, 30, 60, and 100 mg MT/kg diets for 30 days. Later, the fry were
shifted to hapas installed in a pond and then, reared for four months separately. The fish
were fed with the control diet. The results showed that the highest male population
(93.6%) was observed in the fish treated with a 60 mg MT/kg diet, while the lowest
(82.6%) was observed in the fish treated with a 30 mg MT/kg diet. The results also
showed that the fish fed with a 60 mg MT/kg diet had significantly higher mean body
weight (24.1±1.40 g), specific growth rate (2.5±0.10%), feed conversion ratio (1.3±0.10),
and protein efficiency ratio (0.63±0.11) than the untreated fish treated (control) group. In
conclusion, a 60 mg MT/kg diet can be considered as an optimal and economically viable
dose for Nile tilapia sex reversal along with its optimum growth and feed utilization
performances.

INTRODUCTION

Among several cultivable fish species, tilapia
has been identified as the second most important
aquaculture fish species in the world,
particularly in the tropical and sub-tropical
countries next to carp (El-Sayed, 2006; Dagne et
al., 2013). It is also considered as one of the
most important traded fish in the world (Kyule
et al., 2014; Magbanua and Ragaza, 2022).
Farmed tilapia production increased
significantly from 383,654 tons in the 1990s to

4,514,615 tons of production in 2020 (FAO,
2022). Basically, for optimal production
performance of the semi-intensive fish culture,
high quality fish feed are the most preferred due
to their good palatability and digestibility
required for body maintenance, growth,
reproduction and health (Howlader et al., 2023).

Although Nile tilapia has such good
characteristics, its precocious and prolific
reproduction and early sexual maturation of
female has become one of the main challenges

East African Journal of Biophysical and Computational Sciences

Journal homepage : https://journals.hu.edu.et/hu-journals/index.php/eajbcs
Hawassa University

College of Natural & Computational Sciences

Year 2021

Volume xx No xx

Effect of 17α-Methyl Testosterone on Sex Reversal and Growth Performance of Nile tilapia,

 
Research article



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32

for considering this species for commercial
aquaculture (Chakraborty and Benerjee, 2012;
Munguti et al., 2014). This resulted in the
reduction of growth rate at the onset of sexual
maturation and the production of a large number
of fry/fingerlings (Munguti et al., 2014).
Considering the differential growth patterns of
males and females, all-male Nile tilapia
production has been given better consideration
as males are capable of showing a better growth
rate and food conversion efficiency
(Chakraborty and Banerjee, 2012). It is in this
context, production of all-male populations of
Nile tilapia is vital for increasing fish
production under low management practices
(El-Sayed, 2006). Among the various
techniques employed, hormonal sex-reversal has
been considered as an effective method
(Ferdous and Ali, 2011; Jamila et al., 2017).
Even though it is the most important method,
reports of different authors are not consistent
(Wahby and Shalaby, 2010; Celik et al., 2011;
Lakshmi, 2015). Celik et al. (2011) reported that
the efficiency of such a method can be affected
by different environments, feeding rates, and
feeding management, and overall production
management. Hence, the evaluation of such
method in a specific production environment is
crucial. Thus, the main objective of this study
was to find out an optimum dose of 17α-methyl
testosterone on the proportion of Nile tilapia
male population along with growth performance
and feed utilization efficiency of Nile tilapia
under a semi-intensive production system.

MATERIALS AND METHODS

Experimental setup

The experiment was carried out at Ziway
Fishery and Other Aquatic Life Research

Centre, Ziway. The research Centre is situated
at 163 km Southeast direction of Addis Ababa,
the capital city of Ethiopia. It is located at 7o52'
to 8o8' N latitude and 38o40' to 38o56' E
longitude, at an altitude of 1636 m above sea
level. For this study, indoor and outdoor
experimental setups were used. For the indoor
experiment, four fibre glass tanks each with a
size of 2000 ML were prepared. Within each
tank, three plastic circular shape jars with 5 L
capacity were installed for hormone-treated feed
trial experiments. For the outdoor experiment,
12 hapas with 1.5 m x 2 m x 1 m size were
installed in a concrete pond. Before installation
of the hapas, the pond was dried for one week
and then, refilled with water at depth of 90 cm.

Source of experimental fish and feed
formulation

Sexually matured Nile tilapia broodstock that
measured 200 to 250 g body weight were
selected from the holding tank of the Ziway
research centre and immediately transferred into
hapas with 1.5 m x 2 m x 1 m size installed in a
pond at a stocking density of 4 fish/hapas with a
sex ratio of 1 male to 3 females for mating
(ref.). From these hapas, newly hatched Nile
tilapia fry were collected and transferred in
plastic bottles having 5 L water holding capacity
for feed trial experiments. The experiment was
conducted in triplicates with four treatments
(i.e., 0, 30, 60, and 100 mg MT/kg of diets).

Fish diet was formulated by mixing 43% of
fishmeal, 36% of Niger cake, 10% of wheat
bran, 7% of white corn flour, 2% of vitamins
and mineral premix, and 2% of sunflower oil,
having 38% of crude protein. Later, the mixed
ingredients was divided into four groups, in
which the first one was not treated with 17α-



East Afr. J. Biophys. Comput. Sci. (2023), Vol. 4, No. 2, 31-42

33

methyl testosterone (0 mg MT/kg of diets) was
used as a control diet, while the remaining three
groups were treated with 30, 60 and 100 mg MT
dissolved in 95% ethanol per kilogram diet and
were used as tested diets. The control diet was
also mixed with the same amount of ethanol
without hormone. Then, the diets were dried at
room temperature for 24 hours and were stored
in a refrigerator (Celik et al., 2011).

Indoor and outdoor experiments

Immediately after hatching, 300 newly hatched
fry collected from the hapas were transferred
into 12 plastic bottles installed in 4 fiberglass
rearing tanks for three days of acclimatization.
Later, after hatching 240 fry, 20 fry per plastic
bottle, with an average body weight of 0.05 g
were distributed in 12 plastic bottles having 5 L
water holding capacity installed in four
fiberglass rearing tanks in triplicates and reared
for one month. To facilitate water circulation,
the bottles were provided with small holes
which were less than the size of the fry. The fry
were, then, fed four times at 8:00, 12:00 and
16:00 and 18:00 hours a day with 0 mg MT, 30
mg MT, 60 mg MT and 100 mg MT/kg diets
having 38% crude protein for 30 days at 20% of
their body weight (Shamsuddin et al. (2012).
Early morning, uneaten food and faecal matter
were removed daily using siphoning. Oxygen
was provided to each tank using aerators. After
30 days of treatment, total body weight of the all
fry were measured and then transferred and
stocked in hapas with a size of 1.5 m x 2 m x 1
m installed in the grow-out pond at an average
stocking density of 18 fish per hapa and reared
for four months. During this time, the fish were
fed three times at 9:00, 13:00 and 17:00 hours a
day with a control diet at 10% of their body
weight (Mugo-Bundi (2013). The overall

research procedure was approved by the
research committee of Hawassa University and
thus, all applicable international and national
guidelines for the care of animals and use of
animals were followed by the authors.

Data collection and sex determination

Every 15 days (2 weeks) of interval, individual
body weight and body length of hormone-
treated fish stocked in plastic bottles were
recorded early morning. The mortality of the fry
was recorded daily. Similarly, every 15 days of
interval, individual body weight and body
length of the experimental fish stocked in hapa
were recorded. At the end of the experiment (on
week 16, i.e. harvesting week), the final body
weight and body length of all the fish were
recorded. In addition, the sex of each fish was
identified based on external and internal
observation of the sex organs of the fish. Iodion
solution as dye was used to differentiating the
sex of the fish when the secondary sexual
characters were found difficult to differentiate.
Ten fish per treatment were dissected and the
morphology of the gonads was examined and
recorded. Water quality parameters such as
water temperature, pH, dissolved oxygen,
conductivity, and total dissolved solid were
measured using Potable Multi-Parameter Kit.

Following final body weight and length
measurements, calculation of growth parameters
were performed using the following formula
described by Eyo et al. (2013).

I. Calculation of growth and feed utilization
efficiency:
o Body weight gain (BWG) = Final body

weight (FBW) – Initial body weight (IBW)



East Afr. J. Biophys. Comput. Sci. (2023), Vol. 4, No. 2, 31-42

34

o Daily growth rate (DGR) = Weight
gain/Number of experimental days

o Specific growth rate (SGR % per day) =
((LnFBW- LnIBW)/ Number of days) *100

II. Calculation of feed utilization efficiency:
 Food conversion ratio (FCR) = Amount of

dry food intake/Weight gain
 Protein efficiency ratio (PER) = Weight

gain/amount of crude protein

III. Calculation of survival rate, condition
factors and fish yield (put Ref. for each
formula):
 Survival rate (SR%) = Number of harvested

fish/Number of stocked fish *100
 Condition factor (CF) = Final body weight/

(Length3) x 100
 Total production = (No. of fish harvested ×

FBW/Area of rearing place) x10000 m2 x
production cycle

Statistical analysis

Based on the data recorded and calculated
values basic statistics were computed using
SPSS 20 version after the data were tested for
normality and equal variance. The statistical
significance among growth parameters and sex
ratio of fish fed with different test diets were
computed using one-way ANOVA (Analysis of

Variance) in the SPSS. Significance was
assigned at a 5% level of probability. For
between mean treatments significant variation,
was performed using Tukey HSD standardized
range test α = 0.05 level of significance as
described according to El Greisy and El-Gamal
(2012).

RESULTS

Indoor growth and survival rate of Fry

The mean body length and weight of fry at
stocking and after 30 days of hormone treatment
of all groups are presented in Table 1. The
initial mean body length and body weight of fry
were the same (1.3 cm and 0.05 g). After one
month of rearing, the length of fry ranged from
3.3±0.12 cm (30 mg MT/kg diet) to 3.7±0.30
cm (60 mg MT/kg diet) while the mean body
weight of the fry ranged from 0.81±0.18 g (60
mg MT/kg diet) to 0.84±0.13 g (control diet).
Additionally, the survival rate of the fish in
different treatments was high, ranging from
88.2±2.1 to 92.2±1.6%. In all cases, there was
no significant (P > 0.05) difference in survival
rates among the treatments (Table 1).

Table 1: Mean body size parameters with standard error (Mean + SE) of fry at stoking and after
30 days of oral administration with different doses of 17α-methyl testosterone (17α-MT).

Parameters
Treatments

0 mg MT/kg
diet

30 mg MT/kg
diet

60 mg MT/kg
diet

100 mg
MT/kg diet

Initial body length (cm) 1.3±0.37 1.3±0.37 1.3±0.37 1.3±0.37
Initial body length (g) 0.05±0.02 0.05±0.02 0.05±0.02 0.05±0.02
Body length (cm) after 30 days of treatment 3.4±0.20a 3.3±0.12a 3.7±0.30a 3.4±0.20a

Body weight (g) after 30 days of treatment 0.84±0.13a 0.82±0.20 a 0.81±0.18a 0.82±0.15a

Survival rate (SR%) 90.2±1.4a 90.2±1.2a 92.2±1.6a 88.2±2.1a

Note: Values with the same letter across a row are not significantly different (P > 0.05)



East Afr. J. Biophys. Comput. Sci. (2023), Vol. 4, No. 2, 31-42

35

Effects of MT on sex ration

The sex ratio of Nile tilapia fed with hormone-
treated diets is presented in Table 2. The gonad
differentiation of fish fed with the MT-treated
diets gave a higher male proportion than fish fed
with the control diet. The maximum male
population (93.6%) was observed for the fish
fed with a 60 mg MT/kg diet followed by a 100

mg MT/kg diet (86.7%), while the lowest male
population was observed for the fish fed with
the control diet (54.3%). The results showed
that the fish fed with a 60 mg MT/kg diet
produced significantly (P < 0.05) higher male
population than the other groups while the fish
fed with the control diet produced the least
significant.

Table 2: Percentage of male population of Nile tilapia produced after oral administration with
different doses of 17α-methyl testosterone (17α-MT).
Dose of MT Male % P value
0 mg MT/kg (control) diet 54.3a 0.35
30 mg MT/kg diet 82.6b < 0.001
60 mg MT/kg diet 93.6c < 0.001
100 mg MT/kg diet 86.7b 0.005
Note: Values with the same letter across column are not significantly different (P > 0.05)

Outdoor growth performance

The different growth parameters such as mean
body weight gain, daily growth rate, and
specific growth rate, and feed utilization
efficiency such as feed conversion ratio and
protein efficiency ratio of Nile tilapia fed with
different doses of MT-treated diets are presented
in Table 3. The results showed that the highest
mean body weight (24.1±1.4 g) and body
weight gain (24.0±1.2 g) were recorded in the
fish fed with 60 mg MT/kg diet followed by 100
mg MT/kg diet (19.1±0.8 g and 19.0±0.2 g),
while the lowest (14.3±1.8 g) and 14.2±0.1 g)
was observed for the fish fed with a control diet,
respectively. Similarly, the highest mean body

length (11.1±1.2 cm) was observed for the fish
fed with 60 mg MT/kg diet, followed by
10.2±1.2 cm mean body length of fish fed
with100 mg MT/kg diet, while the lowest
(9.1±0.79 cm) was observed for the fish fed
with control diet (Table 3). The results also
showed that the fish fed with hormone treated
diets had significantly (P < 0.05) higher final
mean body weight, in which the fish fed with 60
mg MT/kg diet had significantly (P < 0.05)
higher final mean body weight, and mean
weight gain than at least from the fish fed with
the control diet. Figure 1 also showed the
growth trend of body weight of the fish, in
which fish body weight increased steadily for
the first six weeks, and then, the rate of growth
slightly increased.



East Afr. J. Biophys. Comput. Sci. (2023), Vol. 4, No. 2, 31-42

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Table 3: Mean growth parameters with standard error (Mean + SE) of Nile tilapia treated with
different doses of 17α-methyl testosterone (17α-MT).

Parameters
Treatments

0 mg MT/kg diet 30 mg MT/kg diet 60 mg MT/kg diet 100 mg MT/kg diet

Initial body length (cm/fish) 1.3±0.37a 1.3±0.37a 1.3±0.37a 1.3±0.37a

Initial body weight (g/fish) 0.05±0.02a 0.05±0.02a 0.05±0.02a 0.05±0.02a

Final body length (cm/fish) 9.1±0.79a 9.6±1.03a 11.1±1.19a 10.2±1.17a

Final body weight (g/fish) 14.3±1.84a 18.3±2.46b 24.1±1.38b 19.1 ±0.79b

Body weight gain (g/fish) 14.2±0.02a 18.2±0.02b 24.0±0.21c 19.0±0.21b

Daily growth rate (g/fish/day) 0.12±0.01a 0.15±0.01ab 0.20±0.1b 0.18±0.01ab

Specific growth rate (%/fish/day) 2.2±0.2a 2.3±0.01ab 2.5±0.1b 2.4±0.1ab

Note: Values with the same letter across rows are not significantly different (P > 0.05)

The results also showed that the fish fed with

hormone treated diets had significantly (P <

0.05) higher final mean body weight, in which

the fish fed with 60 mg MT/kg diet had

significantly (P < 0.05) higher final mean body

weight, and mean weight gain than at least from

the fish fed with the control diet. Figure 1 also

showed the growth trend of body weight of the

fish, in which fish body weight increased

steadily for the first six weeks, and then, the rate

of growth slightly increased.

Figure 1: The trend of mean weight of different group of Nile tilapia reared in hapa installed in pond,
where W0 to W16 are rearing times in weeks at two weeks interval, W0 is for initial week, i.e. week zero,
while W16- week sixteen, i.e. harvesting week



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37

Similarly, the results revealed that the highest
mean daily growth rate (0.20±0.1 g/day) and
specific growth rate (2.5±0.01%/day) were
recorded for the fish fed with 60 mg MT/kg
treated diet than the other groups of fish fed
with different level of MT. They were

significantly different (P < 0.05) at least from
the lowest mean daily growth rate (0.12±0.01
g/day) and specific growth rate (2.2±0.02%/day)
of the fish fed with the control diet. The trend of
daily growth rate and specific growth rate
fluctuated as the rearing period increased
(Figures 2 and 3).

Figure 2: The trend of daily growth rate of different group of Nile tilapia reared in hapa installed in pond

Figure 3: The trend of specific growth rate of different group of Nile tilapia reared in hapa
installed in pond, where W2 to W16 are rearing times in weeks, in which fish sampling wars taken
at two weeks interval, W2 was the first sampling times in which fish were sampled after two weeks
rearing, while W16- week sixteen, i.e. harvesting week.



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Feed utilization efficiency and condition
factor and weight-length relationship

The mean values of feed utilization efficiency
parameters and condition factors of Nile tilapia
fed with a control diet and MT-treated diets are
presented in Table 4. The food conversion ratio
(FCR) of different fish fed with different levels
of MT ranged from 1.3±0.1 to 2.3±0.1, while
from 0.37±0.1 to 0.63±0.11 for protein
efficiency ratio (PER). The best FCR and PER
were obtained for the fish fed with a 60 mg
MT/kg diet and were significantly (P < 0.05)

different at least from the fish fed with the
control diet.

The condition factor of Nile tilapia fed with
control, 30 mg MT, 60 mg MT and 100 mg
MT/kg diets were similar and ranged from
1.8±0.12 to 2.1±0.17. According to cube law,
the ‘b’ values for all groups of fish are in a good
condition. The ‘b’ values ranged from 2.8±0.16
to 2.9±0.14.The results showed that both Futon
condition factor and weight-length relationship
parameters were no significant differences
among groups (Table 4).

Table 4: Mean feed utilization efficiency, condition factor, survival and total production with
standard error (Mean + SE) of Nile tilapia treated with different doses of 17α-methyl testosterone
(17α-MT)

Parameters
Treatments

0 mg MT/kg diet 30 mg MT/kg diet 60 mg MT/kg diet 100 mg MT/kg diet

Food conversion ratio 2.3±0.1a 1.8±0.3b 1.3±0.12b 1.8±0.13b

Protein efficiency ratio 0.37±0.1a 0.48±0.12a 0.63±0.11a 0.50±0.20a

Fulton condition factor 1.9±0.13a 2.1±0.17a 1.8±0.14a 1.8±0.12a

Weight-length relationship 2.8±0.16a 2.9±0.21a 2.9±0.18a 2.9±0.14a

Survival rate (SR%) 100±0.00a 100±0.00a 97.9±0.12a 100±0.00a

Total production (TP kg/ha/y) 2574.3±52.1a 3294.6±42.6b 4338.7±73.2c 3438.2±63.6b

Note: Values with the same letter across row are not significantly different (P > 0.05)

Survival rate of fish and fish production

The survival rate and total production of all the
Nile tilapia groups are presented in Table 4. The
survival rates of different Nile tilapia groups
were similar, ranging from 97.9±1.2% to
100±0.0%, while the total productions of
different groups ranged between 2574.3±52.1
kg/year/ha and 4338.7±73.2 kg/year/ha. The fish
fed with a 60 mg MT/kg diet had significantly
higher total production at least from the fish-fed
with the control diet. The results revealed that as
the amount of MT dose increased from 60 mg

MT/kg to 100 mg MT/kg diet the total fish
production decreased (Table 4).

Water quality parameters

The different water quality parameters (pH,
temperature, dissolved oxygen, total dissolved
solid and conductivity) recorded during the
experimental periods for both indoor and
outdoor experiments are presented in Table 5.
The results of the indoor experiment showed
that the different water parameters across
treatments were similar. The values of
temperature ranged from 24.0±0.3 °C to
24.4±0.5 °C, pH ranged from 7.6±0.4 to 7.8±0.6



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39

and dissolved oxygen from 3.6±0.3 mg/l to
3.8±0.7 mg/l. The values of total dissolved
solids and conductivity also ranged from
448.6±3.4 mg/l to 451.1±3.2 mg/l and from
592.4±2.6 μs/cm to 594.9±2.7 μs/cm,
respectively. However, none of the water quality
parameters were significantly different among
the treatments. For outdoor experiments, the

results showed that the mean values of all water
quality parameters recorded during the
experimental period were optimal (28.5±1.1 °C
for temperature, 8.7±2.0 for pH, 8.7±1.3 mg/l
for dissolved oxygen, 543.3±3.5 mg/l for total
dissolved solid and 721.4±5.27 μs/cm for
conductivity).

Table 5: Mean values of different water quality parameters with standard error (Mean ± SE)
recorded during indoor and outdoor experiments.

Water quality parameters

Indoor experiment Outdoor experiment
Treatments

0 mg
MT/kg diet

30 mg
MT/kg diet

60 mg
MT/kg diet

100 mg
MT/kg diet

Temperature (°C) 24.4±0.5a 24.3±0.4a 24.3±0.4a 24.0±0.3a 28.5±1.1
pH 7.7±0.3a 7.7±0.4a 7.8±0.6a 7.6±0.4 a 8.7±2.0
Dissolved oxygen (mg/l) 3.6±0.3a 3.6±0.8a 3.8±0.5a 3.8±0.7a 8.7±1.3
Total dissolved solid (mg/l) 450.7±3.9a 448.6±4.7a 451.1±4.1a 449.6±5.2a 543.3±3.5
Conductivity (μs/cm) 593.6±3.4a 594.9±2.7a 592.4±2.6a 593.9±3.7a 721.4±5.2

Note: Values with the same letter across raw are not significantly different (P > 0.05).\

DISCUSSION AND CONCLUSIONS

This study demonstrates that the application of 17α
methyl testosterone at 30, 60, and 100 mg per kg
diets produced a higher male population and growth
performance than fish fed with untreated diet.
Among the hormone-treated diets, the fish fed with
60 mg MT/kg diet produced a significantly higher
male population and body growth (P < 0.05) than the
other groups. This result agreed well with the reports
of El-Greisy and Gamal (2012) who reported a
significantly higher male population using 60 mg
MT/kg diet than 40 and 80 mg MT/kg diets. This
result also coincides well with the results of Celik et
al. (2011) and Shamsuddin et al. (2012) who
reported 93.7% and 95% male population, using 60
mg MT/kg diet treated for 28 and 21 days,
respectively. A similar result was reported by
Ferdous and Ali (2011) who observed a maximum
(94.3%) male population using a 60 mg MT/kg diet.
These results are in line with the findings reported

by Marjani et al. (2009) in which higher growth
performance of fish was obtained after hormone
treatment.

The present results also showed a higher male
population (93.6%) for 60 mg MT/kg diet than the
report of Abdul (2007) (89%) and Asad et al. (2010)
(68%) for the same MT doses. On the other hand,
the results of the present study showed a relatively
lower male population as compared with 99-100%
for fish treated with 60 mg MT/kg diet (Vera–Cruz
and Mair, 1994; Smith and Phelps, 2001). Such
differences could be due to differences in
management practices. As also indicated by
Lakshmi (2015) and Sourav (2016) such differences
in male population could be due to factors such as
the level of hormone in the diet, feeding and feeding
frequency, water quality parameters, treatment
duration, size at which the fry is selected for
experimentation and stocking density.



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Different doses of MT resulted in the different
growth rates of Nile tilapia in which fish group
treated with a 60 mg MT/kg diet showed
significantly higher mean body weight, body weight
gain, daily growth rate, and specific growth rate of
Nile tilapia than the other groups. This result is in
agreement with the report of Pechsiri and
Yakupitiyage (2005) and Opiyo et al. (2014), who
observed optimal growth performance of fish when
treated with 60 mg MT/kg diet. Also, the results of
the present study showed that the fish treated with
MT treated diets had significantly higher feed
utilization efficiencies than fish treated with control
diet. Statistically, the fish fed with a 60 mg MT/kg
diet had the best feed utilization efficiency in terms
of feed conversion ratio and protein efficiency ratio.
This implies that 60 mg MT/kg diet promotes better
growth performance, better feed utilization in fish as
also reported by Mugo-Bundi (2013).

The significant growth performance and feed
utilization efficiency of fish fed with MT/kg diets
agreed well with the findings of Howerton et al.
(1992) and Varadaraj et al. (1994) who reported a
higher growth rate in O. mossambicus fed with MT
treated diet than the fish fed untreated diet. The
present results also indicated that the fish treated
with 60 mg MT/kg diet for 30 days showed
maximum growth performance and feed utilization
efficiency than the other groups, and further increase
or decrease of hormone dose do not have much
influence on growth and feed utilization efficiency
in fishes as it seems optimal dose. This result also
coincides with the work of Lakshmi (2015) who
reported faster growth and better feed utilization of
Nile tilapia when treated with a 60 mg MT/kg diet.
El-Greisy and El-Gamal (2012) also reported higher
growth and feed utilization efficiency in fish treated
with 60 mg MT/kg diet than 40 and 80 mg MT/kg
diets. This implies that a 60 mg MT/kg diet is an
optimum dose of MT hormone for optimal
production of male population, better growth and
feed utilization efficiency and can be considered as

an optimal dose for Nile tilapia sex-reversal under
the current production management.

On the other hand, the condition factor of all groups
of Nile tilapia were similar implying that condition
factors were not influenced by MT doses. As stated
by Ayode (2011), the fish from all the treatments
showed isometric growth, implies that all the groups
were in good condition.. The present work also
revealed that Nile tilapia followed the cube law
completely in all groups of fish in which their values
were close to the theoretical value (b = 3). The
length-weight relationship was found to be in a
linear form conforming to the general formula
expressing the relationship between the length and
weight of fishes. This could be due to the fact that
the length-weight relationship of fish varies
depending upon the condition of life in the aquatic
environment (Ighwel et al., 2011), but it is an
important tool that gives information on the growth
pattern of animals. In conclusion, 60 mg MT/kg diet
can be considered as an optimal dose for Nile tilapia
sex reversal along with its optimum growth and feed
utilization performances.

Authorship contribution Statement

Berhanu B, Workagegn KB,  Pavanasam N:
Conceptualization, methodology development,
visualization, data analysis and writing up of the
manuscript. Workagegn KB, and P Natarajan
supervision, validation, formal analysis, writing,
reviewing and editing of the manuscripts

Acknowledgments

The authors would like to acknowledge NORAD-
Hawassa University project for the financial support.
The authors also acknowledge the staff of Ziway
Fishery Research Centre for their technical
assistance.



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41

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.


	Introduction
	Mathematical Model
	Crisp equivalent of multi-objective fuzzy transportation problem
	Solution procedure
	Numerical example
	Discussion of the results

	Conclusion
	Basic Preliminaries

