Dietary Piper sarmentosum Roxb. Extract Modulates Ileal Antioxidant Defense and Microbiome-Metabolome Profiles in Hainan Black Goats

Heat exposure can affect intestinal physiology, but the intestinal effects of dietary Piper sarmentosum Roxb. extract (PSE) in goats remain incompletely characterized. During this summer trial in Hainan, the temperature–humidity index generally exceeded 70. Thirty-six male Hainan black goats were randomly assigned to receive 0 (CON), 200, 400, or 600 mg/kg PSE on a dietary dry-matter basis for 90 days after a 15-day adaptation period. At slaughter, small-intestinal tissues and contents were collected for histomorphometry, microbial profiling, and ileal biochemical assays. Exploratory ileal metabolomics compared CON and PSE400 following inspection of morphological and microbial results. Ileal catalase (CAT) activity was higher in PSE400 and PSE600 than in CON, whereas the other measured redox indices showed no significant overall treatment effects in the primary ANOVA. PSE400 also showed a higher duodenal villus height-to-crypt depth ratio, lower ileal crypt depth, and higher ileal lipase activity and microbial richness than CON (p < 0.05). Metabolomics identified relative feature differences and candidate carbohydrate- and lipid-related annotations. These findings associate dietary PSE with higher ileal CAT activity and accompanying morphological and microbial differences under summer conditions. Metabolomic associations remain exploratory and require independent validation.