Dietary Protein Level in the Practical Diet of Yellowfin Seabream, Acanthopagrus arabicus, Juveniles for Optimum Growth Performance, Survival and Carcass Composition

An experimental feeding trial was conducted to determine the optimum level of dietary protein on growth performance, feed utilization, survival and carcass composition of yellowfin seabream, Acanthopagrus arabicus. Five semi-purified experimental diets were formulated containing 350 (P30), 400 (P35), 450 (P40), 500 (P45) and 550 (P50) grams of protein kg-1 of dry matter. Thirty healthy fish (20.94 +/- 0.81g initial weight) were stocked in each floating net cage (1.5m x 1.5m x 1.5m), with three replicates of each treatment. The diets were fed to visual apparent satiation two times a day for a period of eight weeks. At the end of the trial, P40 appeared to have significant (P<0.05) influence on the growth performance. The percent weight gain, average daily weight gain and specific growth rate (SGR) increased significantly by increasing dietary protein level from P30 to P40 (P <0.05), and further increases in protein level (P45, P50) reduced growth. The best feed conversion ratio (FCR; 1.80 +/- 0.03) was also noted at P40 protein level. No significant (P>0.05) differences were found in the whole fish body proximate composition of protein, ash and moisture fed at different protein levels except for lipid content of fish body influenced significantly (P<0.05) by increasing protein in the diet. The second degree polynomial regression estimates that A. arabicus grows best when fed on a diet containing up to 42% protein in floating net cages.