Tannin Supplementation Alters Foraging Behavior and Spatial Distribution in Beef Cattle

Beef production on chemically uniform grass monocultures can limit nutrient synchrony and contribute to uneven pasture use. We evaluated whether supplementing tannins with bioactive plant secondary compounds improves foraging dynamics and landscape use by beef cattle grazing a meadow bromegrass monoculture in ways aligned with rangeland sustainability. Twenty-four Angus cow–calf pairs were allocated to six 3.6-ha paddocks (four pairs/paddock), randomly assigned to Control (Ctrl; n = 3) or Tannin treatment (TT; n = 3). Animals received 1 kg/cow/day of DDGs, with TT receiving an added 0.4% tannins (2:1 condensed:hydrolyzable). Grazing occurred during four 15-day periods (July–September) across two years. Data were analyzed with mixed-effects models. Tannins did not alter biomass removal or cow weight loss ( p > 0.05). However, TT cows exhibited longer evening grazing (2.9 vs. 2.1 h), fewer standing-to-lying transitions (5.7% vs. 7.3%), and more even spatial grazing distribution (CV = 1.861 vs. 2.13; p < 0.05), and greater water consumption (147 vs. 121 L/day; p < 0.01). Average daily gain of calves was numerically greater in TT compared to Ctrl (1.03 vs. 0.93 kg/day; p = 0.27). Collectively, these shifts promoted by tannins point to enhanced evening intake opportunities and reduced patch overuse, outcomes consistent with improved welfare and more uniform pasture utilization two pillars of sustainable grazing. Increased water demand under tannins highlights a management consideration for arid systems. Overall, moderate tannin inclusion was compatible with sustainable grazing by promoting even pasture use and potentially improving nutrient use efficiency without compromising intake.