Effect of feeding different levels of protein on growth performance, feed utilization and digestive enzyme of grey mullet (Mugil cephalus L)

A growth trial was conducted to evaluate the effect of dietary protein level on growth performance, feed utilization and digestive enzyme activity of Mugil cephalus. Four isocaloric (4 kcal/g) experimental diets were formulated using locally available feed ingredients to contain different protein levels viz., 20, 25, 30 and 35% on DM basis and fed to triplicate groups (P20, P25, P30 and P35) of 25 grey mullet fry (average wt. ranging from 0.76 to 0.84 g), stocked in fibre glass tanks containing filtered brackish water and fed @ 10% BW twice daily. After 125 days of experiment, total weight gain in P20, P25, P30 and P35 were 2.82±0.31, 3.10±0.32, 3.81±0.23 and 3.70±0.16 (g) with corresponding feed conversion ratio of 7.69±0.65, 6.36±0.90, 4.86±0.53 and 6.01±0.25, respectively. The best growth performance and lowest feed conversion ratio (P<0.06) in Mugil cephalus was obtained in group fed with 30% protein diet. Protein and lipid digestibility increased (P<0.01) with increase in dietary protein level. Gut protease and cellulase activity were also significantly increased (P<0.05 and P<0.01) with dietary protein level up to 30%. Therefore, it can be concluded that diet containing 30% protein is optimum for growth and digestibility of Mugil cephalus fry at 4 kcal/g energy level.