Dietary Tea Polyphenols Improve Meat Quality of Finishing Pigs by Enhancing Antioxidant Enzyme Activities and Modulating Gut Microbiota

This study aimed to investigate the effects of dietary tea polyphenols (TPs) supplementation on growth performance and meat quality. A total of 120 pigs ([Yorkshire × Landrace] × Duroc) aged 150 days with similar body weights (74.29 ± 0.55 kg), comprising equal numbers of females and castrated males, were randomly assigned to two treatments, each with three pens of 20 pigs: The Control group received a basal diet, and the TP group received the basal diet supplemented with 2000 mg/kg tea extract containing 15% TP. A 7-day adaptation preceded the 60-day feeding period. At the end of the experiment, the final bodyweight of the pigs was measured and six pigs per treatment were selected for sampling. The results showed that: (1) growth performance did not differ significantly, although feed-to-gain ratio and average daily feed intake were numerically lower in the TP group; (2) carcass weight, backfat thickness, and muscle alanine increased, whereas longissimus dorsi lightness and yellowness decreased (p < 0.05); (3) serum total superoxide dismutase and hepatic catalase and glutathione peroxidase activities increased (p < 0.05); (4) Chao1 richness and Shannon diversity were unchanged, and genus-level PCoA showed partial but non-significant separation of the colonic microbial communities (R = 0.1685, p = 0.090). Nevertheless, TP supplementation selectively altered specific bacterial taxa, with lower relative abundances of Pseudomonadota, Escherichia–Shigella, and Ligilactobacillus and higher relative abundances of Solobacterium, norank_f__p-2534-18B5_gut_group, and [Ruminococcus]_gauvreauii_group; and (5) Catenisphaera was positively correlated with serum total superoxide dismutase activity (p < 0.01), whereas the TP-enriched norank_f__p-2534-18B5_gut_group was positively correlated with muscle alanine content (p < 0.05). This study demonstrates concurrent antioxidant, meat-quality, and microbial responses to a TP-containing diet, supporting mechanistic research on a potential gut–liver–muscle association and refinement of supplementation strategies that balance antioxidant benefits with carcass fat deposition.