Cattle grazing grass monocultures often face declining forage quality in mid to late summer, which can reduce animal performance and lead to uneven grazing near water and feeding areas. This study tested whether adding a moderate amount of a commercial tannin extract to a daily protein supplement could change how beef cows forage across the landscape and how their metabolism responds while grazing smooth bromegrass pastures. Over two summer grazing seasons, cow–calf pairs grazed six fenced paddocks and received dried distillers’ grains each day, with half of the paddocks also receiving tannins mixed into the supplement. We used tracking collars to measure cow behaviors and mapped pasture greenness, forage biomass, slope, and distance to water and feeding stations. Tannin supplementation increased the likelihood that cows resumed grazing after walking, and this response was not associated with ambient temperature, while grazing increased toward dusk, and resting and rumination remained stable. Tannin-supplemented cows used higher normalized difference vegetation index (NDVI) areas more often, indicating greener vegetation, and were more willing to use steeper terrain without reducing forage use. By promoting more continuous grazing and broader pasture exploration, tannin supplementation may improve grazing efficiency and reduce concentrated grazing pressure near key resources. Blood metabolite patterns suggested coordinated metabolic responses consistent with improved resilience. Overall, tannin supplementation may support more efficient pasture use and contribute to more sustainable grazing management.

Read the full article in the Journal of Animal Science.