A Comparative Study on the Effects of β-Glucan and Fucoidan on the Growth, Non-Specific Immunity and Disease Resistance of Litopenaeus vannamei

Polysaccharide β-glucan and algal polysaccharides are two prevalent feed additives, yet comparisons of their effects are scarcely reported. In this investigation, we explored the impacts of feeds supplemented with β-glucan and fucoidan, respectively, on the growth, non-specific immunity and resistance to Vibrio parahaemolyticus infection of juvenile shrimp, Litopenaeus vannamei. β-Glucan from Saccharomyces cerevisiae (brewer′s yeast) (YG) and Euglena gracilis (MG) and fucoidan from Macrocystis pyrifera (AP) were supplemented at a concentration of 0.65 g/kg feed, and a commercial feed (DZ) served as the control, five replicates each treatment. The shrimp individuals, initial mean body weight (1.26±0.02) g, were fed with these diets for 42 days. And then challenged with V. parahaemolyticus for 14 days. Results indicated that shrimp survival rate exceeds 90% among all diets, and that of YG, MG and AP significantly higher than that of control (P < 0.05). YG exhibited significantly higher final weight and specific growth rate than control (P < 0.05). Feed efficiency and digestibility were notably superior among all diets (P < 0.05). Compared to the control, β-glucan and fucoidan supplementation significantly elevated the activity of alkaline phosphatase (AKP), acid phosphatase (ACP), total nitric oxide synthase (T-NOS), lysozyme (LZM), peroxidase (POD) and superoxide dismutase (SOD), total antioxidant capacity (T-AOC), and phenoloxidase (PO) content in shrimp serum. YG and MG demonstrated the most pronounced effects, which was followed by AP. Relative expression abundances of LGBP, SOD, HSP70 and proPO in shrimp hepatopancreas was significantly higher among all diets than those of control (P < 0.05), and β-glucan supplementation caused higher expression of LGBP, SOD and HSP70 than fucoidan supplementation (P < 0.05). Expression abundance of Imd, Relish and Toll in hepatopancreas was significantly upregulated among all diets (P < 0.05), and such upregulation was similar among each other. Along the mTOR signaling pathway, β-glucan supplementation significantly increased the expression of TOR, eIF4E2, eIF4E1α and 4EBP in hepatopancreas compared to control (P < 0.05) while fucoidan supplementation significantly upregulated the expression of TOR and eIF4E2 (P < 0.05). V. parahaemolyticus challenging revealed that β-glucan supplementation varied in improving shrimp survival rate among its sources with yeast-coming β-glucan exhibited the most favorable effect (P < 0.05). Our findings imply that appropriate incorporation of β-glucan and fucoidan into feed can enhance the growth performance, immunity and disease resistance of against L. vannamei with the benefit of yeast-coming β-glucan the most comprehensive.