Digestible protein requirement for Nile tilapia larvae (Oreochromis niloticus) during the sexual reversion

The aim of the work was to determine the digestible protein requirement (PD) for Nile tilapia in the sexual reversion phase, where 1250 larvae were assigned to 25 aquariums (60 L), with five treatments and five replicates in a completly randomized design. The larvae were fed ad libitum, five times a day, with isoenergy, isocalcium, isophophorus rations, with 30, 34, 38, 42 and 46% of PD, and 30 mg/kg of a-metil hormone testosterone. The animals of each experimental unit were counted and weighed at each 15 and 28 days of experiment for evaluation of the survival and average weight. For the average weight of the animals quadratic effect was observed, with point of maximum of 39.06 and 38.56% of PD at 15 and 28 days, respectively. The survival rate linearly decreased as the PD levels increased, at 15 and 28 days. Water temperature, pH, conductivity and dissolved oxygen level presented average-values of 24.60 of 2.02degreesC; 7.34 +/- 0.22; 218.47 +/- 16.29 muS/cm; and 6.38 +/- 1,18 mg/L respectively. The PD requirement of for Nile tilapia in the sexual reversion phase was of 38.6%.