Effects of Ganoderma lucidum Polysaccharides on Dexameth-Asone-Induced Immune Injury in Goslings

This study aimed to investigate the role of ganoderma lucidum polysaccharides (GLP) in mitigating dexamethasone (DEX)-induced immune injury in goslings. Dexamethasone (DEX) is commonly used to establish an animal model of immune suppression, which mimics the immune injury caused by stress or certain pathological conditions in poultry. A total of 180 one-day-old goslings were randomly assigned to three groups: control (Con), DEX, and DEX + GLP, with six replicates of 10 goslings each. The Con and DEX groups were fed a basal diet, whereas the DEX + GLP group received feed supplemented with 0.2% GLP. From days 14 to 21, the DEX and DEX + GLP groups were injected with 3.5 mg/kg body weight (BW) of DEX, while the Con group received normal saline. Growth performance, immune organ indices, serum parameters, organ morphology, and intestinal microbiota were evaluated at 21 and 35 days. At day 21, the Con group exhibited significantly higher BW, average daily gain (ADG), spleen, thymus, and bursa indices, as well as serum total protein (TP), albumin (ALB), globulin (GLOB), IL-6, IgA, and IgG compared to the DEX and DEX + GLP groups (p < 0.01). By day 35, the DEX + GLP group demonstrated greater ADG than the DEX group (p < 0.01) and showed improved TP, ALB, and immune organ indices relative to DEX alone (p < 0.05). Histological analysis indicated that DEX induced bursa plica disorder, spleen parenchyma loosening, and thymus lobule atrophy, all of which were alleviated by GLP supplementation. Regarding the gut microbiota, the Con group displayed higher α-diversity at day 21 than the DEX group (p < 0.05), while at day 35, β-diversity in the DEX group differed markedly from that in the Con and DEX + GLP groups. Furthermore, DEX + GLP was associated with an enrichment of Bacteroidetes, Flavobacterium, and Lactococcus as microbial biomarkers. Overall, GLP effectively mitigated DEX-induced immune injury and partially restored growth performance by improving immune organ morphology, modulating serum factors, and reshaping gut microbiota.