Effects of dietary protein and lipid levels on growth performance, feed utilization and body composition of juvenile giant trevally ( Caranx ignobilis Forsskal, 1775)

Abstract

An 8-week feeding study was carried out to assess the effects of dietary protein and lipid levels on growth, feed utilization and body composition of juvenile giant trevally (Caranx ignobilis Forsskal, 1775). Six diets were produced with three crude protein levels of 42%, 47%, 52% and two crude lipid levels of 10% and 18% in a 3 × 2 factorial design. Treatments were named by their protein and lipid levels, viz. P42:L10, P42:L18, P47:L10, P47:L18, P52:L10 and P52:L18, corresponding P/E of 20.23, 18.73, 22.31, 20.81, 24.63 and 22.12 g/MJ respectively. Growth performance in terms of length, final body weight and specific growth rate were the highest (p < 0.05) when juveniles were fed P52:L10 with P/E of 24.63 g/MJ. The same diet also resulted in the highest effective feed utilization in terms of feed intake and feed conversion ratio. Crude protein in whole body increased when dietary protein or dietary lipid increased from 42% to 52% and 10% to 18% respectively. Significantly increased levels of amino acids in fish's body, including alanine, aspartic acid, glutamine, serine, leucine, threonine, valanine and arginine, were observed in fish fed 52% protein. Increasing dietary lipid from 10% to 18% led to reduced levels of alanine, glutamine, leucine, threonine, valine and arginine in fish. The result suggests that P52:L10 diet with P/E ratio of 24.63 g/MJ subjects the growth requirement of juvenile giant trevally.