Sampling-Age-Associated Cecal Community and Intestinal Transcriptional Responses to Dietary Astragalus Polysaccharides in Taihu Geese

Sampling age-associated microbial and intestinal transcriptional responses to Astragalus polysaccharides (APS) remain unclear in geese. In a 90-day experiment, 150 one-day-old Taihu geese received 0, 100, or 200 mg/kg APS, with five replicate cages per diet. Cecal 16S rRNA gene profiles were obtained at days 30, 60, and 90 (n = 4 per diet and age); ileal and jejunal RNA sequencing was performed at day 90 (n = 4 per diet and tissue). Sampling age explained 15.1% of the Bray–Curtis variation (q = 0.0012), APS explained 6.7% after age adjustment (q = 0.0144), and their interaction was significant (q = 0.0128). Community associations were stable across amplicon sequence variant filtering thresholds; no APS association with alpha diversity or an individual genus survived correction. For 100 and 200 mg/kg APS, respectively, 43 and three ileal genes and nine and seven jejunal genes met q < 0.05 and |log2 fold change| ≥ 1. Jejunal expression was associated with RNA integrity, limiting transcriptomic interpretation. Chicken single-cell markers contextualized part of the ileal signature at 100 mg/kg APS; no diet-adjusted paired microbiome–pathway association survived correction. APS-associated community and transcriptional patterns remain exploratory within the phase-specific feeding program.