Effect of Astragalus polysaccharide and its sulfated derivative on growth performance and immune condition of lipopolysaccharide-treated broilers

This study evaluates the immunomodulating activities of Astragalus polysaccharide (APS) and sulfated APS (SAPS) in LPS-infected broiler chicks. SAPS was derived using the classic chlorosulfonic acid–pyridine method. On day 16, the birds were injected intramuscularly with 0.5 mL of either saline, APS (4 or 8 mg/kg of body weight (BW), shorten as APS-4 or APS-8) or SAPS (4 or 8 mg/kg of BW, shorten as SAPS-4 or SAPS-8) once a day for three successive days. On days 19 and 20, the birds were intraperitoneally injected with 0.5 mL of LPS (1 mg/kg of BW). Saline was used as blank control. Compared with the blank control, LPS-treated birds showed lower daily body weight gain (BWG), average daily feed intake (ADFI), villus height and intraepithelial lymphocytes (IEL) number in jejunum, and higher feed conversion ratio (FCR, feed:gain), spleen index, plasma NO concentration, blood heterophil:lymphocyte (H:L) ratio, and the production of NO in the blood T lymphocytes. Compared with the LPS group, birds in APS-4, SAPS-4 and SAPS-8 groups showed decreased FCR (P < 0.05). Moreover, SAPS increased BWG and jejunal villus height (P < 0.05) at 8 mg/kg BW. Plasma NO concentration was lower in APS-8 group than that in LPS group (P < 0.05). Both APS-8 and SAPS-8 treatments elevated the number of jejunal IEL (P < 0.05), and decreased blood H:L ratio (P < 0.05), respectively. Administration of APS or SAPS did not affect the ADFI, immune organ index, crypt depth and mucosal thickness of the jejunum, and the number of goblet cell. Our findings suggested that APS and SAPS possessed dose-dependent growth-promoting and immunomodulating effect, and was a potential development direction for immunomodulator under early LPS stimulation condition.