Effects of dietary supplementation with β‐glucan and synbiotics on growth, haemolymph chemistry, and intestinal microbiota and morphology in the P acific white shrimp

The goal of this study was to investigate the effects of dietary supplementation with β‐glucan and microencapsulated probiotics ( B acillus subtilis or P ediococcus acidilactici ) on growth performance, body composition, haemolymph constituents, and intestinal morphology and microbiota of the Pacific white shrimp L itopenaeus vannamei . Four treatment diets [basal diet (C), β‐glucan‐containing diet (β‐glu), β‐glucan plus B. subtilis ‐containing diet (β‐glu+ Bs ), and β‐glucan plus P . acidilactici ‐containing diet (β‐glu+ Pa )] were fed to L . vannamei for 90 days. Shrimp fed the β‐glu and β‐glu+ Pa diets exhibited similar growth performance and body protein content, which were significantly higher than those of shrimp fed the control diet ( P  < 0.05). No significant differences in haemolymph triglyceride, cholesterol, protein, haemolymph urea nitrogen or chloride were detected among the experimental diets. However, dietary β‐glucan alone increased the haemolymph glucose level and osmolarity ( P  < 0.05). Synbiotic supplementation had greater effects on intestinal microbiota and morphology than dietary β‐glucan alone. For example, β‐glu+ Bs increased the number of intestinal lactic acid bacteria and decreased the number of Vibrio spp. ( P  < 0.05), and β‐glu+ Pa increased the height of intestinal villi.