Abstract
Tea polyphenols (TPs), bioactive secondary metabolites from Camellia sinensis, demonstrate significant potential for enhancing poultry reproductive efficiency. This 43-week study systematically evaluated graded TPs supplementation (0-500 mg/kg Food Weight) in Tianfu G02 Blue-shell roosters (n = 540) through growth monitoring, histopathological analysis (Hematoxylin and Eosin staining, H&E), and molecular profiling (ELISA, qPCR). The data were analyzed using a sampling T-test or ANOVA and Tukey's Test. Optimal growth performance was achieved at 100-400 mg/kg TP doses, improved daily feed intake and weight gain. The 200 mg/kg cohort exhibited peak spermatogenic capacity at week 28 (sperm density, P < 0.05) and week 43 (motility, P < 0.05), while 300 mg/kg enhanced sperm viability. Paradoxically, 500 mg/kg impaired reproductive parameters (the lowest sperm density, motility and viability). Testicular morphology revealed dose-dependent effects: 300-400 mg/kg groups showed seminiferous tubule expansion with concomitant testosterone elevation. Molecular analyses demonstrated TPs-mediated upregulation of androgen pathway genes (AR, Pgk2, P < 0.05) and antioxidant enhancement (MDA reduction, SOD/GSH-Px activation, P < 0.05). Immune modulation was evidenced by 200 mg/kg-induced immunoglobulin elevation (IgM, IgA, P < 0.05) and cytokine upregulation (IL-1β, IL-2, P < 0.05). Intestinal barrier integrity improved via ZO-1 and Claudin3 expression in 200-300 mg/kg groups (P < 0.05). These findings establish 200-300 mg/kg TPs as the optimal dosage window for enhancing rooster productivity, while cautioning against supra-nutritional (>400 mg/kg) applications.