Effects of different dietary protein and lipid levels on some digestive enzymes activity in juvenile Sobaity Seabream Sparidentex hasta (Valenciennes, 1830)

This study was conducted to compare some digestive enzymes activity in juvenile Sobeity Seabream (S. hasta) under the effects of different dietary protein and lipid levels. 6 dietaries including 3 levels of protein(35, 40 and 45%) and 2 levels of lipid (7 and 14%) were determine in treatments 1 to 6. The fish with mean initial weight of 36.55±0.28 g were randomly stocked in triplicates (10 fish/tank) in eighteen 300 l tanks filled with filtered sea water at 27 ppt. The experimental fish were fed to apparent satiation thrice daily for 56 days. After the treatment period, digestive enzyme activity including total protease, alkaline phosphatase and alphaamylase was calculated. Results reveled that activity of alkaline phosphatase and totalprotease were significantly affected bydietary protein levels whereas alphaamylase activity was not affected significantly by dietary protein. No significant differences in the activity of the alkaline phosphatase and alphaamylase activity were observed at different lipid levels whereas total protease showed a significant increase at 14% lipid. A direct relationship was observed between the increase in alkaline phosphatase activity and the little decreasing trend in alphaamylase enzyme activity on the one hand and the increase in dietary lipid levels on the other hand. The interactionof dietary protein and dietary lipid significantly affected total protease activity. Results showed that efficient use of protein, digestive enzyme activity development, growth improvement and food production cost effectiveness are possible through making a balance between 40% of protein and 14% of lipid in dietary of S. hasta. In addition, determining the ratio of alphaamylaseenzyme activity to proteasecan show fish adaptability to nutrition conditions.