Effects of sulfated β-glucan from Saccharomyces cerevisiae on growth performance, antioxidant ability, nonspecific immunity, and intestinal flora of the red swamp crayfish (Procambarus clarkii)

The aim of this study was to examine the combined effects of sulfated β-Glucan from Saccharomyces cerevisiae (sGSC) on growth performance, antioxidant ability, nonspecific immunity, and intestinal flora of the red swamp crayfish (Procambarus clarkii). Four experimental diets (sGSC25, sGSC50, sGSC100 and sGSC200) with different levels of sGSC (0.025%, 0.05%, 0.1% and 0.2% in diet, respectively) were fed to juvenile crayfish (average weight: 2.5 ± 0.5 g) for 8 weeks. The control diet was given with 2000 mg/kg GSC (GSC200 group). The based control diet was given without sGSC or GSC (blank group). Each group had 3 parallel test pools, 20 crayfish were reared in each pool. At the end of the growth trial, adding dietary 0.025%-0.1% sGSC could significantly improve the growth performance, antioxidant capacity and immunity of crayfish. Compared with GSC, sGSC had a better effect at lower concentration. Higher concentration of sGSC (>0.1%) would cause some side effects. sGSC also could improve the structure of the intestinal flora and optimize the function of the flora. sGSC would increase the abundances of probiotics such as Hafnia and Acinetobacter, and decreases the abundances of maleficent bacteria such as Enterobacteriaceae. Higher concentration of sGSC (>0.1%) would increase the abundance of Aeromonas. To conclude, 0.025%-0.1% sGSC can be used as a supplement in crayfish feed to increase growth, immunity, and antioxidant capacity and improve the structure of intestinal flora. These results provided a theoretical basis for the application of sGSC instead of GSC in crayfish breeding. It will be necessary to further study the optimal concentration of sGSC in feed additives in different growth stages of crayfish in the future.