Amylose and amylopectin levels affect the growth performance and metabolism in pacu Piaractus mesopotamicus

Starch is a complex carbohydrate that is widely used in animal feed, and its structural characteristics may affect its utilization. This study evaluated different amylose and amylopectin levels on carbohydrate metabolism and growth of the frugivorous pacu (Piaractus mesopotamicus). Pacu juveniles (n = 216) were distributed in 24 tanks (130-L) and fed until apparent satiation for 90 days. Six isocaloric and isoproteic diets were formulated with 390 g/kg starch, containing different amylose and amylopectin levels: 0/390, 70/320, 100/290, 200/190, 270/120 and 290/100 (g/kg in the diet). Increases in the final body weight, specific growth rate and protein efficiency ratio were observed in the fish fed the 0/390 and 70/320 diets. The crude lipid content in the whole body and muscle lipid as well as the hepatosomatic index were significantly higher in fish fed the 0/390 diet than in those fed diets with amylose contents higher than 200 g/kg. A reduced hepatic glucokinase activity was observed in fish that received the 270/120 and 290/100 diets. This study suggests that diets with more than 300 g/kg amylopectin and less than 100 g/kg amylose result in increases in starch utilization and growth in pacu.