Lysine and methionine supplementation in diets with low protein level for the initial growth of pacu <em>Piaractus mesopotamicus</em> (Holmberg)

Abstract

The objective of this research was to study the effects of methionine or lysine supplementation in diets with low protein level for growth of pacu Piaractus mesopotamicus (Holmberg) (Characiformes, Characidae). Diets were formulated as a basal diet presenting 22% crude protein (CP), 4100 kcal gross energy (GE)/kg, 0.42% of methionine and 1.16% of lysine and other six diets, with the same basic formulation, supplemented with 0.2%, 0.4% or 0.6% methionine or lysine. An eighth diet (control) contained 26% CP, 4100 kcal (GE)/kg, 0.48% methionine and 1.43% of lysine. The diets were administered ad libitum to 144 fingerlings with initial medium weight of 14.98 ± 1.16 g. Averages weight gain, gross energy efficiency retention and feed intake for the control treatment were significantly higher (P < 0.05) than those of smaller protein level diets. Averages protein retention efficiency were only higher (P < 0.01) in the diets supplemented with lysine, showing the advantages of lysine supplementation in diets with low crude protein level. A higher growth of pacu was confirmed with diets containing 26% of CP.