Effect of APS on IEL number (A–C) and GC (D–F) number in experimental Muscovy ducklings. Sections stained with HE at 2, 3, 4, 6, 9 and 15 dpi were selected from each experimental group (n = 6) for intestinal immunocyte count, including IEL and GC. Bars without the same superscripts (a–c) mean significant differences (P < 0.05). Abbreviations: APG, APS pretreatment for the MDRV-infected group; APS, Astragalus polysaccharide; CIG, cohabitation infection group; GC, goblet cell; IEL, intraepithelial lymphocyte; NCG, normal control group.