Long-Term Dietary Supplementation with Quebracho-Derived Condensed Tannin in Growing–Finishing Pigs: Effects on Growth Performance, Ascaris suum Infection, Intestinal Bacterial Community Structure and Meat Quality

Although condensed tannins have shown antiparasitic, antioxidant, and microbiota-modulating effects, their long-term effects on growing–finishing pigs remain unclear. In this study, 24 pigs were randomly assigned at 43 days of age to a control group fed a basal diet or a treatment group supplemented with 0.75% commercial quebracho tannin (MGM-P) for 16 weeks. The effects on A. suum infection, growth performance, fecal microbial community structure, and pork quality were evaluated. The results showed that egg counts, adult worm counts, and the number of infected pigs were not significantly different between groups (p > 0.1). No differences were observed between groups in growth performance, meat texture, juiciness, or fatty acid composition (p > 0.1). Denaturing gradient gel electrophoresis (DGGE) analysis indicated altered fecal microbial community structure in the MGM-P group. The longissimus dorsi from the MGM-P group showed lower lightness and hue angle (p < 0.05), and free amino acids associated with bitter taste, including valine and leucine, also tended to decrease (0.05 < p < 0.1). These findings indicate that long-term supplementation with 0.75% MGM-P did not influence growth performance or overall meat quality in growing–finishing pigs; its efficacy against A. suum infection was limited under the natural infection conditions of this study.