Effect of dietary fructooligosaccharide supplementation on growth, body composition, hematological and immunological parameters of Asian seabass (Lates calcarifer)

A feeding trial to study the effect of addition of prebiotic fructooligosaccharide (FOS) on feeds for juvenile Asian seabass (Lates calcarifer) (12.2 +/- 0.4 g) was carried out. Five isonitrogenous and isocaloric experimental diets were formulated that contained 400 g kg(-1) protein and 90 g kg(-1) lipid. The FOS was supplemented at 2.5, 5, 7.5 and 10 g kg(-1) in the diet of L. calcarifer with a control that was devoid of FOS. The trial was carried out in 1000-L fiber reinforced polymer (FRP) tanks with three replicates (each containing 20 fish) for each treatment. After 45 days of feeding, it was observed that FOS supplementation at 10 g kg(-1) in the diet resulted in significantly (P < 0.05) higher final biomass (334.2 +/- 7.3 g) and survival (97.7 +/- 3.8 %). There were no significant (P > 0.05) differences in biological indices of fish fed with the experimental and control diets. Whole body chemical composition of animals post-feeding revealed significantly (P < 0.05) higher crude protein, crude lipid and total ash content in 5 g kg(-1) FOS-supplemented diet. The analysis of hematological parameters revealed that red blood cells (RBC), white blood cells, hemoglobin, packed cell volume, mean corpuscular volume, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration levels increased significantly (P < 0.05) with dietary FOS supplementation up to 5 g kg(-1).The second-degree polynomial regression analysis of RBC (4.06 +/- 0.05 x 10(6) mm(-3)) showed that FOS 5 g kg(-1) is an optimal level in seabass diet. Significantly (P < 0.05) higher lysozyme (77.4 +/- 0.5 U mL(-1)) and superoxide dismutase (75.2 +/- 0.3 U mL(-1)) activity was recorded at 10 g kg(-1) FOS supplementation. It could therefore be concluded that 10 g kg(-1) FOS supplementation has a beneficial effect in improving the survival rate and immunological parameters in L. calcarifer juveniles.