Effect of long term administration of dietary β-glucan on immunity, growth and survival of Labeo rohita fingerlings

Abstract

β-glucan at different dietary doses was administered to enhance the immunity, growth and survival against Aeromonas hydrophila and Edwardsiella tarda in Labeo rohita fingerlings. Four different Diets with 0, 100, 250 or 500 mg of β-glucan kg − 1 diet were fed to L. rohita fingerlings for 56 days. Biochemical and haematological parameters such as serum total protein content, albumin content, globulin content, albulin : globulin ratio, glucose content and leucocyte counts as well as cellular immune parameters such as superoxide anion production, phagocytic activities, lymphokine production index and humoral immune parameters such as lysozyme activity, complement activity and serum bactericidal activity in the fish were evaluated at two week intervals. After 56 days, the specific growth rate (SGR) and food conversion ratio (FCR) were calculated and fish were divided into two subgroups under each major treatment group for challenge with A. hydrophila and E. tarda. The mortality (%) and agglutinating antibody titre were recorded on the 28th day after challenge. Immune parameters including the leucocyte count, phagocytic ratio, phagocytic index, lysozyme activity, complement activity and serum bactericidal activity rose to their highest levels on 42 days after feeding with the diet containing 250 mg of β-glucan kg − 1 diet. This dose also resulted in the highest protection in the challenge study. Doses of 250 and 500 mg of β-glucan kg − 1 diet resulted in better SGR and FCR. Thus, administration of 250 mg of β-glucan kg − 1 diet is recommended for enhancement of immunity, growth and survival of L. rohita fingerlings.