EFFECTS OF DIETARY β-1,3-GLUCAN ON GROWTH PERFORMANCE, SERUM METABOLITE, IMMUNE-RELATED GENE EXPRESSION AND RESISTANCE TO NITRITE STRESS IN LITOPENAEUS VANNAMEI

To investigate the effects of dietary β-1,3-glucan on growth performance, serum metabolite, immune-related gene and resistance to nitrite stress in Litopenaeus vannamei, 0.1% β-1,3-Glucan was supplemented to a basal diet (control, G0) with different feeding schedules: permanently β-1,3-glucan diet (G1), 7 days β-1,3 glucan diet-7 days of control diet (G2) and 14 days β-1,3 glucan diet-14 days of control diet (G3). After the feeding trial, these shrimps were exposed to nitrite-N (20 mg/L) for 120h. The results showed that dietary β-1,3-glucan had no significant effect on growth performance and whole-body composition after 84d feeding trial (P>0.05). The activity of lipase in hepatopancreas in G2 and G3 groups was significantly higher than that in G0 and G1 groups (P<0.05). The shrimp in G1, G2 and G3 groups had significantly higher hemolymph triacylglycerols and cholesterol levels than G0 group (P<0.05). Higher expression levels of LPS/b-glucan binding protein (LGBP), Prophenoloxidase (proPO) and superoxide dismutase (SOD) were observed in G3 group compared to G0 and G1 groups (P<0.05). After 120h nitrite-N stress, the mortality in G3 group was significantly lower than that of G0, G1 and G2 groups (P<0.05). Nitrite stress significantly reduced the levels of GLU, GOT and GPT and significantly enhanced hemolymph level. G3 group had significantly higher expression levels of LGBP, proPO and SOD compared to G0 group (P<0.05). The expression level of serine proteinase in G1 group was significantly higher than that in G0, G2 and G3 groups (P<0.05). L. vannamei fed diet G3 can improve nitrite resistance probably by accelerating energy metabolism and increasing expression levels of LGBP, proPO and SOD.