International Journal of Aquaculture, 2013, Vol.3, No.23, 133
-
137
http://ija.sophiapublisher.com
135
study further showed that
T. terrestris
has no negative
effect on the survival of
O. niloticus
.
The steady
weight gain observed during the phase one of this
experiment, with increase in
T. terrestris
inclusion, is similar
to the observations of Kavitha and Subramanian (2011),
Cek et al. (2007a) and Cek et al. (2007b) on
Peocilia
latipinna
,
P. reticulata
and
Cichlasoma nigrofasciatum
respectively. They all reported that fish had better
growth rate with increase in the concentration of
T.
terrestris
in culture water.
Tribulus terrestris
has
been reported by (Akram et al., 2011) to be a
testosterone enhancer,
T. terrestris
treated fish showed
better growth rates with increase in the levels of
T.
terrestris
.
This agrees with the report of Mateen (2007)
that since the androgens have both sex reversal and
anabolic effects, the sex reversed tilapia shows a
better growth performance as compared to untreated
tilapia.
2.2
Water Quality Parameters
Temperature ranged between 26
℃
to 28
℃
,
pH
ranged from 7.7 to 8.2, Dissolved oxygen was from
5.13
mg/L to 9.12 mg/L, Nitrite and ammonia both
ranged from 0.001 mg/L to 0.044 mg/L and 0.030 mg/L
to 0.142 mg/L. Temperature of the pond ranged from
26
℃
to 28
℃
,
the pH of the pond water was between
7.7
and 7.9, dissolved oxygen ranged from 6.25 mg/L
to 9.12 mg/L, Nitirte and Ammonia were between
0.06
mg/L to 0.12 mg/L and 8.71 mg/L to 12.82 mg/L
respectively. These water quality parameters of the
experimental set up are in conformity with the
requirements for adequate growth of
O. niloticus
as reported
by Omitoyin (2007) and Soto-Zarazúa et al. (2010).
These water quality parameters are in conformity with
the requirements for adequate growth of fish as
reported by Omitoyin (2007).
2.3
Sex Reversal Ratio
It is believed that
T. terrestris
affects androgen
metabolism, significantly increasing testosterone or
testosterone precursor levels (Neychev and Mitev, 2005)
and oral administration of
T. terrestris
increased
sexual behavior in male rats (Gauthaman et al., 2002).
In this study, the inclusion of MT and
T. terrestris
extract to the fish feed contrary to the addition of
T.
terrestris
in the culture water by Kavitha and
Subramanian (2011) and Cek et al. (2007a) showed
similar results. As against the usual 1:1 ratio of males
to females of
O. niloticus
,
the treatment with 0.0g/kg
of
T. terrestris
extract gave a ratio of 1:2 (males to
female); the percentage of males was however,
significantly higher than females in all
T. terrestris
and MT treated fish. The percentage of males recorded
in the MT treated fish in this experiment was 73%
which is similar to the results obtained by Marjani
et al. (2009) at the same concentration for Mozambique
tilapia. Kavitha and Subramanian (2011), Cek et al.
(2007
a; 2007b) and Kavitha et al. (2012) also reported
that percentage of males increased with increase in the
concentration of
T. terrestris
in
Peocilia latipinna, P.
reticulata
and
Cichlasoma nigrofasciatum
.
Tribulus
terrestris
treated 0-day-old larvae showed successful
sex reversal and spermatogenesis than untreated
progenies.
In the present study, there was a higher recorded
percentage of males, growth rates and better feed
conversion ratio in the fish treated with
T. terrestris
at
2.0
g/kg concentration which compares very well with
those recorded for the fish treated with MT. It can
therefore be concluded that 2.0 g/kg and above
concentration of
T. terrestris
can be used successfully
to induce sex reversal in
O. niloticus
in place of MT
which is more expensive, unavailable and has public
health issues related to its use.
3
Materials and Method
3.1
Fry Production
Five pairs of broodstocks of
Oreochromis niloticus
(350
±25.8) g were collected from the Department of
Aquaculture and Fisheries Management Fish Farm,
University of Ibadan and stocked at a ratio of 1:1
(
male to female) in 1m X 1m hapas and monitored
regularly for fertilized eggs. After 21 days, fertilized
eggs were noticed in the mouth of the fish and were
collected and incubated in the hatchery for (18-32) hrs.
The hatchlings were transferred to the laboratory 24 hrs
after hatching.
3.2
Extracts Procurement and Feed Preparation
Tribulus terrestris
extract (Trib 60) was procured from
Tonvara Premium Natural Supplements, United
Kingdom. The extract contained 60% protodioscin,
while the 17-α-methyltestosterone which was used as
control was purchased from Kingdom Aquarium
Nigeria Ltd, Lagos, Nigeria.
A 50% crude protein diet was prepared using soy bean