Optimal dietary protein level for pacu Piaractus mesopotamicus juveniles reared in biofloc system

This study evaluated the effects of dietary protein levels on growth performance, hematological and biochemical parameters, carcass and fillet yields, somatic indexes, and body chemical composition of pacu juveniles reared in a biofloc system over a 60-day period. Five isoenergetic (13.4 MJ kg(-1) DE) experimental diets were formulated with increasing crude protein (CP) levels (194, 232, 278, 316, and 359 g kg(-1)). Three hundred fish weighing an average of 3.16 +/- 0.3 g were randomly distributed in 20 experimental tanks (50 L) at the rate of 15 fish per replicate and fed experimental diets until apparent satiation four times a day. The experimental design was completely randomized with five treatments and four replicates. Weight gain (WG), thermal growth coefficient (TGC), protein productive value (PPV), and fillet yield (FY) showed quadratic effect (P < 0.05) as protein levels increased. Feed consumption (FC) and carcass yield (CY) showed a linear growth (P < 0.05), while protein efficiency ratio (PER) decreased linearly (P < 0.05) as protein levels increased. The hematological and biochemical parameters did not differ between treatments (P > 0.05), except for the hematocrit. However, blood parameters remained at normal range for this species. The optimal dietary protein level was estimated at 310 g kg(-1) CP (approximate to 268 g kg(-1) DP) for the best growth of pacu juveniles reared in the biofloc system.