Submitted to: Oregon State University Extension Publications
Publication Type: Government Publication
Publication Acceptance Date: 12/10/2011
Publication Date: 12/20/2011
Citation: Johnson, D.D., Davies, K.W., Cooke, R.F. 2011. Grazing behavioral responses of beef cattle to medusahead invasion in sagebrush steppe rangelands. Oregon Beef Council Report. Oregon State University Extension Publications. p. 65-68. Interpretive Summary: Medusahead invasion decreases biodiversity, reduces livestock forage production, and degrades wildlife habitat. However, little is known about the effects of medusahead invasion on cattle grazing behavior. We evaluated livestock grazing behavior with GPS collars in bunchgrass rangelands interspersed with medusahead infestations. We also measured nutritional quality of medusahead and bunchgrasses to correlate with grazing behavior. Preliminary results suggest that differences in grazing preference may be tied to differences in nutritional quality. Preliminary results also suggest that most of the time cattle prefer bunchgrasses to medusahead, but there may be times in the spring when cattle will be more likely to consume medusahead. This information can be used by land managers and ranchers to assist them in planning grazing management for medusahead-invaded rangelands.
Technical Abstract: The objectives of this study are to determine: 1) seasonal forage quality of medusahead-invaded rangeland relative to adjacent rangeland supporting desirable vegetation; 2) relative grazing preference of beef cattle for medusahead-invaded rangeland and adjacent rangeland supporting desirable vegetation; 3) seasonal cattle behavioral responses to medusahead invasion. Rangeland pastures (1000 to 3500 acres) in southeast Oregon containing both areas of substantial, near monotypic infestations of medusahead and areas of remnant, intact desirable vegetation (seed or native range grasses) were selected for the study. All areas (patches) principally comprised of medusahead and areas of desirable rangeland vegetation were identified and mapped in each study field during the summer of 2010. The study employed global positioning system (GPS) collars to measure seasonal behavioral responses of beef cattle to medusahead invasion. Cattle grazed the study fields continuously, season long (~April through September) to allow determination of seasonal variation in grazing behavior. Concurrent with collection of cattle behavioral information, composite forage quality samples were gathered on a biweekly schedule during the trial from five randomly selected medusahead patches and five paired areas of intact desirable rangeland vegetation (crested wheatgrass) within each study field. Forage samples were analyzed for crude protein content, acid detergent fiber, neutral detergent fiber, and total digestible nutrient content to determine relative seasonal variation in forage quality of medusahead and desirable rangeland vegetation to aid in the interpretation of cattle grazing behavior. Forage quality information from the Happy Valley site in 2010 indicated a significant separation between medusahead and crested wheatgrass in crude protein and total digestible nutrient content throughout the majority of the growing season. Variation in forage quality between medusahead and desirable rangeland vegetation may help to explain cattle grazing behavioral responses to medusahead invasion