The free-choice feed and regulation of protein intake were investigated in juveniles reverted males of tilápia do Nilo, Oreochromis niloticus. During the experiment 1000 fish (reverted males) with similar weigth and length were maintained in eight aquariuns supplied with recirculated water (groups of 125 fish each aquarium). Fish were fed by demand-feeders, containing the two experimental diets, formulated to contain 15% and 40% protein each and distributed in four treatments (A: 15% protein diet on one hand and 40% protein diet on the other hand, B: alike in A, therefore with an inversion on both hands, C: the two feeders supplied with 15% protein diet, D the two feeders supplied with 40% protein diet) The Latin Square was the estatistical method used for the experiment, and the treatments were distributed into four stages (I, II, III and IV). A one week stop after each stage was stipulated and the fish received a 30% protein diet. The results showed that no differences about the intake was detected between fish fed by diets containing 15% and 40% protein in the same aquarium. However, with same diets in the tanks ( Treatment C and D), the animals that were fed with the 15% protein diet showed better feed intake. The percentage of regulated protein during the experiment was about 24% protein. The results confirm the hipoteses of free-choice ability by tilápia-do-Nilo to detect the level of protein in the diet.
feed behaviour; free choice; Nile Tilápia; Oreochromis niloticus; protein
