The increasing demand for animal-derived protein driven by population growth, together with concerns about microbial resistance associated with the use of antibiotics as growth promoters, highlights the need for alternative strategies to sustain high productivity. Among these alternatives, natural additives, plant extracts, and their bioactive compounds—particularly polyphenols such as condensed tannins (CT)—have received increasing attention. This study aimed to evaluate whether the addition of tannin extract rich in CT could serve as a viable growth-promoting alternative in cattle. Thirty-two intact male cattle were used in a 104-day feedlot trial. Animals were allocated to four experimental groups: T0 (control, no additive), and T15, T30, and T45, receiving 15, 30, and 45 g tannin extract rich in CT/day, respectively. Throughout the experimental period, body weight, feed intake, blood parameters (hematology, biochemistry, oxidative status, and immune indicators), ruminal traits (pH, protozoal counts, volatile fatty acid profile, and microbiota), and meat characteristics (chemical composition and fatty acid profile) were evaluated. The T15 group showed greater average daily gain (ADG) than T0 (P = 0.01), and regression analysis indicated an estimated optimal dose of 20 g tannin extract rich in CT/animal/day (P = 0.01). Feed efficiency was also higher in T15 compared with T0 (P = 0.02). No differences were observed in carcass weight or dressing percentage among treatments (P > 0.05). In terms of digestibility, T15 showed higher ether extract digestibility (P = 0.05), whereas T45 reduced digestibility of dry matter (P = 0.05), crude protein (P = 0.04), and neutral detergent fiber compared with T0. Ruminal fluid from T15 (P = 0.05) and T30 (P = 0.01) showed higher total volatile fatty acid concentrations than T0, mainly due to increased acetate and propionate levels. Tannin extract intake also affected ruminal protozoal counts, indicating a modulatory effect of the additive on rumen microbial dynamics. Inclusion in diet of 15 and 30 g tannin extract/day increased circulating immunoglobulin concentrations (P ≤ 0.05) and reduced ceruloplasmin levels compared with T0 (P = 0.02). Meat from T45 animals showed higher proportions of saturated fatty acids (P = 0.05), lower monounsaturated fatty acids (P = 0.05), and greater lipid peroxidation compared with T0 (P ≤ 0.05). Overall, tannin extract rich in CT intake per cattle showed potential to improve productive performance and animal health, particularly through antioxidant, anti-inflammatory, immunological, ruminal fermentation, and nutritional responses. However, addition at 45 g/day impaired nutrient digestibility and meat quality, suggesting that excessive tannin extract rich in CT intake may induce pro-oxidative and pro-inflammatory effects.
Brunetto et al. (Fri,) studied this question.