Abstract
In response to the urgent need for alternatives to antibiotics in poultry production, this study evaluated the effects of ursolic acid (UA), a plant-derived triterpenoid, on growth performance, metabolism, intestinal function, and antioxidant capacity in broilers. A total of 320 Cobb broilers were randomly divided into four groups: a control group and three groups supplemented with UA at 0, 50, 200, or 400 mg/kg of diet, with 8 replicates of 10 birds each, over a 42-day period. Body weight and feed intake were measured on days 21 and 42. On day 42, samples were collected for enzyme-linked immunosorbent assay (ELISA), untargeted metabolomics, hematoxylin-eosin (H&E) staining, meat quality assessment, and quantitative real-time PCR (qRT-PCR) analyses. Data were analyzed using one-way analysis of variance (ANOVA) in SPSS, and orthogonal contrasts were used to assess linear and quadratic responses to UA. The results showed that UA supplementation significantly enhanced growth and slaughter performance (P < 0.05), increased serum total protein (P < 0.05), and reduced serum triglycerides (P < 0.05). Untargeted metabolomics indicated that 200 mg/kg UA modulated lipid metabolism via α-linolenic acid and glycerophospholipid pathways. Additionally, this dose significantly improved the villus height-to-crypt depth ratio (VH/CD) and ileal protease activity (P < 0.05). Both 200 and 400 mg/kg UA reduced the b45min value of breast muscle (P < 0.05). Furthermore, UA supplementation elevated antioxidant enzyme activities in serum and ileum (P < 0.05). At the molecular level, 200 mg/kg UA upregulated expression of amino acid and fatty acid transporter genes, downregulated kelch-like ECH-associated protein 1 (KEAP1) (P < 0.05), and enhanced expression of catalase (CAT), superoxide dismutase 1 (SOD1), nuclear factor E2-related factor 2 (NRF2), and NAD(P)H: quinone oxidoreductase (NQO1) (P < 0.05). In conclusion, UA effectively improved growth performance, metabolic health, intestinal function, and antioxidant capacity in broilers, demonstrating its potential as a safe and effective alternative to conventional growth promoters in poultry production.