EFFECT OF PROTEIN LEVEL AND HAPA EXCHANGE TIMES ON GROWTH PERFORMANCE AND PROFITABILITY OF NILE TILAPIA (OREOCHROMIS NILOTICUS) FRY DURING SEX REVERSAL STAGE IN COMMERCIAL HATCHERY, FAYOUM GOVERNORATE, EGYPT

Two trials were conducted for three weeks )one during June and the other during July 2014( to evaluate the effect of protein level and hapa exchange times on growth performance and profitability of Nile tilapia (Oreochromis niloticus)fries during sex reversal stage in a commercial hatchery, Fayoum governorate, Egypt.  The first one was conducted in six hapa (2 per each treatment) with size of 10.2 m³(4 × 3 × 0.85 m). The hapas were stocked with Nile tilapia fry at a rate of 50,000 fry/hapa. Three diets varying in protein level [fish meal as animal protein source] were formed as follows: the D₇₂ [100% fish meal (FM) = 72 % Crude Protein (CP)]; the D₅₃ (70% FM + 30% wheat flour = 53% CP) and D37₇ (33.33% FM + 33.33 % wheat flour + 33.33 % commercial diets = 37% CP). The diets were offered to the fry five times/day at a rate of 30% of total biomass weight/first week then decreased gradually by 10% every week. The second trial was to study the effect of hapa exchange times [zero time (0TT); one time (1TT) and two times (2TT) treatments, where, every treatment had two replicates] on the fry growth performance. The fry were fed with D37₇ (37% CP) which was mentioned previously at the first trail at the same feeding rate and times/day. The hapas of both first and second trails were fixed in an earthen pond (3000 m²).
The results obtained from the first trail revealed that significant differences (P≤0.05) were found for all growth performance parameters .The D₇₂ has the best values for final weight, weight gain, daily gain, specific growth rate. On the other hand, survival rate and feed conversion ratio have an opposite trend for that treatment (D₇₂) when it was compared with the other treatments.  But the profit index (PI) was significantly higher (P ≤ 0.05) for fish fed D₃₇ followed by D₅₃ and finally D₇₂.
The results of the second trail demonstrated that there were significant differences (P≤0.05) for all growth parameters the best values was obtained with both 1TT and 2TT when were compared with 0TT.