EFFECTS OF DIFFERENT LEVELS OF DIETARY PROTEIN AND LIPIDS ON GROWTH PERFORMANCE AND DIGESTIVE ENZYMES OF RABBITFISH Siganus rivulatus REARED IN WELL WATER

Rabbitfish (Siganus rivulatus) is a potential candidate for warm water marine aquaculture production . Until now, rabbitfish aquaculture has not produced on a commercial scale.  That may  be due to lack of knowledge of its nutritional requirements. Moreover,  inadequate protein and lipid levels in the diet lead to  an  impaired growth.  Thus,  the determination of the suitable ratio of protein to energy in fish diet is important.  Accordingly, the purpose of this study was to determine optimal protein to lipid ratio and its effect on growth  performance and digestive enzymes of S. rivulatus.

A 2×2 factorial feeding trial was  carried out.  Four  semi-purified diets containing 2 protein levels (30 % and 40%) and 2 lipid levels (6 % and 12 %) were formulated and fed to triplicate groups of Rabbitfish ( S. rivulatus ) juveniles (0.32 ± 0.16 g /fish) for 56 days.

   Fish fed on P40L12 and P40L6 diets gave the best final weight (FW), weight gain ratio (WGR), daily gain index (DGI) and specific growth rate (SGR), followed by P30L6 and P30L12  (Table 1). The dietary levels of protein and lipids have been well reflected on the digestive enzymes of fish (Table 2). The highest value of protease has been recorded at P40 with both lipid levels followed by P30L12 .  Fish fed on P30L6, P30L12, P40L6 to P40L12, respectively, showed an increase in lipase upward. The highest result of amylase has been detected in P30L6  followed by P30L6 and P40L6. The highest value of glutamate dehydrogenase has been given at P30L6 and then the results were plateaued.