Effects of Bacillus amyloliquefaciens on Growth Performance, Immune Performance, Antioxidant Capacity, Jejunal Microbiota and Transcriptome of Zi Geese.

With the global ban on antibiotic growth promoters, identifying safe, effective alternatives for poultry production is urgent. Probiotics, particularly Bacillus amyloliquefaciens (BA), have shown promise in improving animal health and performance, but research in geese remains limited. This study aimed to evaluate the effects of dietary BA supplementation on growth performance, immune function, antioxidant capacity, intestinal morphology, microbiota, and transcriptome in growing Zi geese. A total of 180 50-day-old male Zi geese were randomly assigned to a control group (basal diet) or an experimental group (basal diet supplemented with 1 × 108 CFU/g BA) for 40 days. Growth performance, serum immune indices, intestinal antioxidant parameters, morphology, jejunal microbiota, and transcriptomic profiles were assessed. BA supplementation significantly increased average daily gain and decreased feed-to-gain ratio (p < 0.01). Serum IgA, IgG, IgM, and IL-4 increased, while IL-2, IL-1β, and TNF-α decreased (p < 0.01). Intestinal CAT, GSH-Px, and T-AOC increased (CAT in duodenum and jejunum, p < 0.01; CAT in ileum, p < 0.05; GSH-Px in duodenum and ileum, p < 0.01; GSH-Px in jejunum, p < 0.05; T-AOC in all segments, p < 0.01), and jejunal MDA decreased (p < 0.01). Villus height and V/C ratio improved. Jejunal microbial diversity increased, with higher Proteobacteria and lower Pseudomonas and Escherichia-Shigella. Transcriptomic analysis revealed DEGs enriched in calcium signaling, cell junction, and intestinal barrier pathways. Dietary BA at 1 × 108 CFU/g enhances growth, immunity, and intestinal health in Zi geese by improving gut function, remodeling microbiota, and modulating gene expression, supporting its use as a green feed additive.