Effects of dietary protein and energy levels on growth, feed utilization and body composition of cuneate drum (Nibea miichthioides)

An 8-week experiment was conducted in net pens to assess the effects of dietary protein and energy levels on growth, feed utilization and body composition of cuneate drum. Cuneate drum (initial body weight 19 g fish− 1) were fed 9 feeds formulated to contain 3 levels of digestible protein (DP 36%, 38% and 40%) and 3 levels of digestible energy (DE 14, 16 and 18 MJ kg− 1). Groups of fish were fed raw fish (Sardinella spp.) to serve as a commercial control. Specific growth rate (SGR), final body weight (FBW), feed intake, feed conversion ratio (FCR), energy retention efficiency (ERE), and moisture and protein contents in carcass of the fish were significantly affected by DP and DE levels. Nitrogen retention efficiency (NRE) was dependent on DP level, and lipid and ash contents in carcass of the fish were affected by DE level. Specific growth rate and FBW of fish fed feeds with the same DE level increased when DP increased from 36% to 40%, whereas SGR and FBW of fish fed the feeds formulated at the same DP level increased when dietary DE increased from 14 to 16 MJ kg− 1. No improvement, or even a slight decline in SGR and FBW, occurred with the further increase of DE to 18 MJ kg− 1. For the same DP level, NRE and ERE increased with the increase in DE from 14 to 16 MJ kg− 1. Carcass lipid content of fish fed the feeds with the same DP level increased with the increase in DE level. There were no significant differences in SGR, FBW, feed intake, FCR, and protein and lipid contents in carcass of fish fed the raw fish and feed containing 40% DP and 16 MJ kg− 1 DE. Nitrogen retention efficiency and ERE were higher for fish fed the formulated feed containing 40% DP and 16 MJ kg− 1 DE than fish fed the raw fish.