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Suboptimal brood-rearing habitat often limits sage-grouse (Centrocercus urophasianus) populations in western North America. In many mountain big sagebrush (Artemisia tridentata�ssp.�vaseyana) brood-rearing habitats, sagebrush is too dense (> 10-25%) and limits the understory forbs and arthropods that sage-grouse prefer to eat during summer. We investigated whether protein supplementation could concentrate cattle grazing or trampling during late fall to reduce mountain big sagebrush canopy cover and increase the diversity and abundance of forbs and arthropods. We applied targeted cattle grazing within three large, contiguous pastures (about 715 ha each) in the Beaverhead Mountains of southwestern Montana. Dry cows (190-210 cows per pasture) simultaneously grazed the three pastures at a light stocking rate and low stock density for two weeks in mid-October 2015. In each pasture prior to cattle grazing, we selected one 4-ha macroplot of dense sagebrush. Next, within each macroplot we identified eight 78.5-m2 microsites where mountain big sagebrush canopy cover exceeded 30%. We placed a low-moisture block protein supplement in the center of four microsites per macroplot, whereas the remaining four microsites per macroplot comprised the untreated control. Vegetation and arthropod response was quantified in early summer 2016. Mountain big sagebrush canopy cover was 71% less in treated vs. untreated microsites (11% vs. 38% canopy cover, respectively;�P�< 0.001). Bite count observations indicated that sagebrush cover was reduced by cattle trampling rather than browsing, as sagebrush comprised < 1% of cattle diets. Forb diversity was 13% greater in treated microsites (P�= 0.094), forb species richness was 16% greater in treated microsites (P�= 0.044), and forb composition trended higher in treated microsites (45% of herbaceous composition in treated microsites vs. 32% in untreated microsites;�P�= 0.106). Our results indicate that protein supplementation during late fall can concentrate cattle trampling sufficiently to enhance sage-grouse brood-rearing habitat.