Fall Grazing with Sheep Decreases Sagebrush and Improves Biodiversity

Many areas in the Western United States are dominated by sagebrush. The increase in sagebrush density over the past century is generally attributed to: 1) reduced numbers of mixed feeders and browsers such as deer, antelope, goats and sheep, 2) increased numbers of cattle and elk, 3) repeatedly grazing the same grasses and forbs, particularly during spring, and 4) fire suppression.

Though the decline in diversity is due in part to grazing, grazing may in fact be the answer to improving plant diversity and wildlife habitat in sagebrush-steppe ecosystems. Grazing by sheep during the fall, when grasses and forbs are dormant, can increase diversity by reducing sagebrush’s competitive advantage. Supplemental nutrients can improve the effectiveness of fall grazing because sheep and goats supplemented with energy and protein eat nearly twice as much sagebrush as unsupplemented animals. The energy and protein supplements enable sheep to better detoxify the toxins found in sagebrush. Thus, intake of sagebrush may be increased if large numbers of supplemented sheep graze sagebrush for a few days in the fall.

Graduate students Tyler Staggs and Ryan Woodland, and professor Neil West in the Department of Forest, Range and Wildlife Sciences at Utah State University conducted studies to determine if supplementation and high-density, short-duration fall grazing would increase diversity in plant communities dominated by sagebrush. Their study was conducted at Deseret Land and Livestock in Rich County, UT. Their results indicate fall grazing and supplementation with energy and protein reduced sagebrush abundance and increased biodiversity.

The study above was conducted on small pastures (.62 acres) with permanent fences. For this technique to be effective, producers must be able to use livestock to browse large areas of sagebrush either using herding or temporary electric fence. In 2006, graduate student Michael Guttery, range extension specialist Roger Banner and professors Fred Provenza and Terry Messmer also from USU conducted a study to determine the feasibility of browsing sagebrush with supplemented sheep on at a larger scale. They grazed eight 8-acre plots with 1000 mature ewes from mid-October to the end of November on sagebrush dominated rangeland on Utah’s Parker Mountain. A 35-acre demonstration site was also browsed by 1200 yearling ewes from mid-November to mid-December on Blue Mountain near Vernal, UT. Ewes received a pelleted supplement of 30% corn, 5% soybean meal, 45% alfalfa and 20% beet pulp. On Parker Mountain, ewes were supplemented at a rate of 2 to 3 lbs/hd/day and on Blue Mountain yearling ewes received 1.7 lbs/hd/day. The supplement not only helped sheep consume more sagebrush but was also used to flush them. Sagebrush was heavily browsed during the study. The photo above shows the level of heavy browsing most plants received. The objective of this study is to determine if supplementation and high-density, short-duration fall grazing by sheep will increase biodiversity and improve habitat for sage grouse on sagebrush dominated rangeland. The study will also track reproductive performance of ewes and compare costs of grazing treatments with traditional rangeland treatments such as mechanical or chemical methods.

This project is funded by the USDA-NRCS/USU Sage-grouse Restoration Project.