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ARS Home » Pacific West Area » Dubois, Idaho » Range Sheep Production Efficiency Research » Research » Publications at this Location » Publication #166192

Title: CONSEQUENCES OF SELECTING RAMBOUILLET EWES FOR MOUNTAIN BIG SAGEBRUSH (ARTEMISIA TRIDENTATA SSP. VASEYANA) DIETARY PREFERENCE

Author
item Seefeldt, Steven

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2005
Publication Date: 6/15/2005
Citation: Seefeldt, S.S. 2005. Consequences of selecting Rambouillet ewes for mountain big sagebrush (Artemisia Tridentata SSP. Vaseyaba)dietary preference. Rangeland Ecology and Management. 58:380-384.

Interpretive Summary: Over time mountain big sagebrush can develop very dense stands. The problem with these dense stands is that they reduce forage and increase fire risk. Reducing the density of these stands by standard methods with fire, herbicides, and mechanical means is often risky and expensive. Research was conducted to determine if sheep that had been selected with a high dietary preference for mountain big sagebrush would reduce the density of mountain big sagebrush compared to sheep with a low dietary preference for mountain big sagebrush. After three years of October grazing it was determined that the two groups of sheep did not reduce mountain big sagebrush density any more than pastures that were not grazed. The sheep with a high preference for mountain big sagebrush, however, consumed more antelope bitterbrush than low preference sheep. Antelope bitterbrush is an important rangeland species; therefore increased grazing of this plant by sheep has negative environmental consequences. The results of this research highlight the complexity of changing dietary preferences in animals. Care must be taken to determine unintended consequences on other plant species from animals selected with different dietary preferences.

Technical 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.