الفهرس 
Nutritional requirementsOnly 14 pages are availabe for public view
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Abstract
Two trials were conducted with Nile tilapia Oreochromis niloticus
larvae and fry at Commercial fish hatchery In Fayoum Governorate and on
the shores of lake Qarun. The first was conducted to study the effect of
storage conditions for treated feeds with male hormone 17 α -
methyltestosterone (light condition, store temperature and time after
prepared) on the rates of sex reversal, survival % and growth performance.
Brood fish of Oreochromis niloticus were allowed to breed naturally in
hapas (4×7m) with water depth of about 80 cm, the hapas are placed in an
earthen pond with area of 4200m2, during 2019 with a sex ratio of 3
female's to1 male; about 5000 of the newly hatched fry were stocked in a
hapa (2×1m, and water height of 80 cm). No significant difference among
the stored methyltestosterone (MT) treated diets (clear and dark vessels and
placed in the refrigerator or in the room temperature) and ability to sex-
reverse fry, the highest sex reversal % was in treated diet with hormone and
refrigerated for use 97.5% and prepared daily 96.27%. Basal diets (free of
MT hormone) came lower in the rate of male sex reversal. The results of this
trial indicate that the rates of male sexual transformation in Nile tilapia
larvae were affected by the method of preparing treated feed hormone,
especially preservation temperature and the time after preparing, although
this effect was limited, where the quality of the hatchery is measured by the
high percentage of males resulting from sex reversal, regardless of the
significance between the treatments.
The second experiment was performed to study the effect of Tribulus
terrestris powder on sexual transformation (sex reversal), compared to the
male hormone 17 α-methyltestosterone in addition to tracking growth and
feed utilization parameters in the same condition of the first experiment.
Significant increase (P≤ 0.05) in percent male was observed with increasing
Tribulus terrestris powder in the diets, while the worst in sex reversal for
male was the control treatment, growth results showed no significant
differences between all parameter during 28 day on the contrary of nursery
stage, treatment 200 g/kg diet gave a higher Weight gain (g), Final weight
(g), specific growth rate (SGR) and best feed conversion ratio (FCR). There
are significant differences (P≤ 0.05) between treatments containing male
hormone 17 α -methyltestosterone and basal diet regarding sex reversal for
males which the better treatments were with those containing the different
doses of male hormone, MT growth results showed significant differences
(P≤ 0.05) between the treatments (28 day or 90 day). The results of this trial
refer to the recommendation that the Tribulus terrestris powder at 200
mg/kg diet and 17 α Methyl testosterone at 150 mg/kg diet are the most
effective for sex reversal in Nile tilapia larvae.
Key words: Nile tilapia, sex reversal, Tribulus terrestris, growth
performance, feed utilization, male hormone.