Influence of dietary protein levels on growth performance and body composition of African bonytongue fingerlings,Heterotis niloticus(Cuvier, 1829)

Two experiments were conducted to examine the influence of dietary protein levels on growth and carcass proximate composition of Heterotis fingerlings. Four isoenergetic practical diets were formulated to contain dietary protein levels from 250 to 400 g kg−1 diet. Replicate groups of young Heterotis (initial live weight 3.96 and 26.40 g in experiments 1 and 2 respectively) were handfed twice daily to apparent satiation for a period of 42 and 28 days respectively. Statistical analysis revealed that growth rate was significantly affected by dietary protein level (P < 0.01). The highest weight gain was observed in fingerlings fed with 300 and 350 g protein kg−1 diet for fish size ranging between 3–15 and 26–62 g respectively. There was no significant difference between groups fed with 300, 350 and 400 g protein kg−1 diet for Heterotis fingerlings (3–15 g) in the one hand; in the other hand, significant differences were found between fish (26–62 g) fed with 350 g protein kg−1 diet and those receiving 300 and 400 g protein kg−1 diet, with no significant difference between each other. The specific growth rate varied from 2.4% to 3.1% day−1. The whole-body protein, lipid, moisture and ash contents were not significantly affected by dietary protein levels (P > 0.05). The relationships between percentage weight gain and dietary protein levels suggested very similar dietary protein requirement (about 310 g crude protein kg−1 diet) for Heterotis ranging from 3 to 62 g. The maximum growth occurred at about 345 g protein kg−1 diet.