Study on preparation and effect of oligoβ-glucan and oligochitosan on immune stimulation white patches in the internal organs disease on Tra catfish (Pangasianodon hypophthalmus)

Oligoβ-glucan and oligochitosan were prepared by gamma Co-60 irradiation of β-glucan/H₂O₂ and chitosan/H₂O₂ solution. The efficiency of the degradation process was determined by gel permeation chromatography (GPC) method. Results showed that the Mw decreased with increasing concentration of H₂O₂ and doses. For oligoβ-glucan, Mw reduced from 56.7 kDa to 7.1 kDa when β-glucan 10%/H₂O₂ 1% solution was irradiated at 14 kGy. For oligochitosan, Mw reduced from 45.5 kDa to 5.0 kDa when chitosan 5%/H₂O₂ 0.5% solution was irradiated at 21 kGy. Tra catfish (Pangasianodon hypophthalmus) was fed with oligoβ-glucan and oligochitosan in various concentrations of 0, 50, 100, and 200 mg/kg feed for 45 days and then was challenged with Edwardsiella ictaluri bacteria to investigate immune stimulation effect against white patches in the internal organs disease. The results indicated that oligoβ-glucan and oligochitosan exhibited good immune stimulation effect with optimum concentration of 100 mg/kg feed. Survival rate of Tra catfishes fed with oligochitosan and oligoβ-glucan is 47.62 ± 1.96% and 46.67 ± 2.58%, respectively. In addition, the mixture of oligochitosan 50 mg/kg + oligo?-glucan 50 mg/kg showed the highest survival rate (62.22 ± 1.96%). (author)