Growth and haematology of pacu, Piaractus mesopotamicus, fed diets with varying protein to energy ratio

Haematopoiesis and blood cells' functions can be influenced by dietary concentration of nutrients. This paper studied the effects of dietary protein:energy ratio on the growth and haematology of pacu, Piaractus mesopotamicus . Fingerling pacu (15.5±0.4 g) were fed twice a day for 10 weeks until apparent saciety with diets containing 220, 260, 300, 340 or 380 g kg^?1 crude protein (CP) and 10.88, 11.72, 12.55, 13.39, 14.22 MJ kg^?1 digestible energy (DE) in a totally randomized experimental design, 5 × 5 factorial scheme ( n =3). Weight gain and specific growth rate were affected ( P <0.05) by protein level only. Protein efficiency ratio decreased ( P <0.05) with increasing dietary protein at all levels of dietary energy. Daily feed intake decreased ( P <0.05) with increasing dietary energy. Mean corpuscular haemoglobin concentration was affected ( P <0.05) by DE and interaction between dietary CP and DE. Total plasma protein increased ( P <0.05) with dietary protein and energy levels. Plasma glucose decreased ( P <0.05) with increasing dietary protein. The CP requirement and optimum protein:energy ratio for weight gain of pacu fingerlings, determined using broken-line model, were 271 g kg^?1 and 22.18 g CP MJ^?1 DE respectively. All dietary CP and DE levels studied did not pose damages to fish health.