Study on effect of immune stimulation of γ-ray irradiated β-glucan on tilapia

Abstract

Low molecular weight β-glucan (LMWβG) and oligoβ-glucan solution were prepared by the hydrothermal steaming combination with  γ-irradiation method. The efficiency of the degradation process was demonstrated by gel permeation chromatography (GPC) analysis of the average molecular weight (Mw) of β-glucan. Results showed that the Mw decreased with increasing steaming time, concentration of  H₂O₂ and doses. For LMWβG, Mw reduced from 296,600 Da to 44,400 Da when concentration of H₂O₂ raises from 0 to 10 % and for oligoβ-glucan Mw reduced from 56,700 to 7,100 Da at 16 kGy. Tilapia fish was fed with LMWβand oligoβ-glucan of 100 mg/kg feed for 45 days and then was challenged with  Streptococcus agalactiae  bacterial to investigate immune stimulation.  The results indicated that oligoβ-glucan has higher immune stimulation effect compared to LMWβG. The effect of oligoβ-glucan with various concentrations of 50, 100 and 150 mg/kg feed was investigated. Results showed that the highest survival rate was attained for oligoβ-glucan of 150 mg/kg as feed additive.