Abstract:
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.