Consequences of selecting Rambouillet ewes for mountain big sagebrush dietary preference. Van Vleet, Stephen^*,1, Seefeldt, Steven¹, ¹ USDA/ARS, Dubois, ID, USA

ABSTRACT- Mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana [Rydb] Beetle) canopies can become too dense. A dense sagebrush canopy suppresses other vegetation needed for grazing. Rambouillet ewes that were selected with high and low dietary preferences for mountain big sagebrush were tested for their ability to reduce the cover of dense stands of sagebrush. Eighty ewes with high and low preferences for mountain big sagebrush were grazed in October on 8 pastures with a 33% shrub cover for 3 years. Even though fecal near infrared reflectance spectroscopy measurements indicated that high preference ewes consumed more mountain big sagebrush than did low preference ewes (P > 0.005), there was no difference in the reduction of sagebrush canopy between the high- and low-preference ewes. Indeed, grazing did not reduce mountain big sagebrush more than what occurred in the ungrazed pastures. However, ewes with a high preference for mountain big sagebrush reduced antelope bitterbrush (Purshia tridentata (Pursh) DC.) canopy more (P > 0.05) than did low preference ewes (30 cm and 10 cm, respectively). In this study, the selection of ewes with a dietary preference for mountain big sagebrush had the unintended consequence of selecting ewes with a dietary preference for antelope bitterbrush. Antelope bitterbrush is a desirable shrub in sagebrush steppe ecosystems and reductions in antelope bitterbrush due to altered livestock preferences will reduce rangeland health.

KEY WORDS: mountain big sagebrush, diet preference, sheep, antelope bitterbrush