Sources and levels of crude protein in diets for pacu (Piaractus mesopotamicus) fingerlings.
A 100-day experiment was carried out with 288 fingerlings of pacu, assigned to 36, 100-litre cement containers, 8 per unit, to evaluate the replacement of fish flour by soyabean meal and protein levels in the diets. During the experimental period, average water temperature was 28°C and dissolved oxygen, pH, alkalinity and conductivity remained within adequate levels for the development of this species. The experimental design consisted of randomized blocks, with nine treatments in a 3×3 factorial arrangement, 3 levels of crude protein (22, 26 and 30%) and three levels of fish meal replacement by soyabean meal (0, 50 and 100%). The results showed that 26% of crude protein was better and that fish meal can be partially or totally replaced by soyabean meal without affecting fingerling weight gain, feed to gain, specific growth rate and protein efficiency rate. Body composition, nitrogen retention efficiency, and body nitrogen and fat were not influenced by protein source.