الفهرس 
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Abstract
The experimental work was conducted in fish research laboratory, faculty of agriculture, kafr EL-Seikh, Tanta university ina cooperation with physiology laboratory, Animal production Department, faculty of agriculture, El-Mansoura university.
A set of 2400 of nile tilapia fry(oreochromis niloticus)wth average initial weight of 0.020g, at six days of age were collected from a private fish farm in Kafr El-Sheikh governorate, Egypt. The fry were randomly divided into 24 similar groups and stocked in the experimental aquaria (100 fry in each ). Experimenal groups (24)were assigned to the MT hormonal treatments at concentratons of 0.20,40.80, 160 and 320 mg/kg feed for 21 and 56 days (2 groups/treatment).
Two basal diets were formulated to contains 45 and 35% crude protein (CP). All experimental fish groups were fed on the basal diet contained 45%CP in a powder form during thr first 7 weeks, while the fish were received a diet containing 35% CP in a 1 mm pelleted form during the other 18 weeks of the experimental period.the obtained results were as the following :
The sex reversal ratio: the optimum level of 17Q-MT hormone used in tilapia sex reversal was 40mg/kg feed and increasing MT level above 40mg/kg feed resulted in decreasing percentages of male produced.
Growth performance :The hormonal treatment and periods of treatment did not affect significantly on the growth performances of tilapia fish.