EFFECTS OF DIETARY PROTEIN AND LIPID ON GROWTH PERFORMANCE AND BODY COMPOSITION OF ADVANCED FIGERLING BLACK CARP(MYLOPHARYNGODON PICEUS)

To investigate the effects of dietary protein and lipid on growth and body composition of advanced fingerling black carp (Mylopharyngodon piceus), ten trial diets for a 52 factorial experiment, formulated with five protein levels (30%, 33%, 36%, 39% and 42%) and two lipid levels (6% and 9%), were fed to triplicate groups of black carp (initial average weight 95.54 g/fish) for 70 days. We observed that weight gain increased with increasing dietary protein level up to 39% (P0.05), but did not increase further with increasing dietary protein level to 42% (P0.05). Accordingly, feed conversion ratio decreased with increasing dietary protein level from 30% to 39% and kept stable with further increasing dietary protein level to 42%; protein efficiency ratio, protein retention and viscera somatic index tended to decrease with increasing dietary protein level; analysis of weight gain data by a broken line regression model showed that the optimum dietary protein level required for the maximum growth of black carp was 40% of dry diet. Dietary lipid level and the interaction of dietary protein and lipid did not affect weight gain and feed utilization (P0.05); levels of dietary protein or lipid and their interaction did not affect the survival, body profile index, hepato-somatic index and condition factor (P0.05); fish viscera-somatic index and muscle lipid had an increasing tendency with the decrease of dietary protein level; fish fed diets with a dietary lipid level of 9% had higher whole body and muscle lipid than those of fish fed diets with a dietary lipid level of 6% (P0.05). It could be concluded that 40% dietary protein and 6% dietary lipid are suitable for maintaining good growth performance. Low dietary protein and high dietary lipid may cause extra body lipid deposition.