Season-long grazing of seeded cool-season pastures in the Northern Great Plains

In the semi-arid Northern Great Plains, seeded cool-season grasses are prim arily recommended for spring and fall grazing because their nutritive quali ty is perceived as too low to support acceptable animal weight gains during mid-summer. This perception is caused in part by traditional use of high s pring stocking rates, which leave little forage remaining for mid-summer us e. A study was conducted near Mandan, N.D. to determine the effect of moder ate (1.6 AUM ha(-1)) and heavy (2.4 AUM ha(-1)) stocking rates on weight ga ins of yearling Hereford steers grazing crested wheatgrass (Agropyron deser torum [Fisch. Ex Link] Schult.), western wheatgrass (Pascopyrum smithii [Ry db.] Love), smooth bromegrass (Bromus inermis Leyss.) and flat (class II an d III) and rolling (class IV and VI) native rangelands. Studies were conduc ted over a 140-day grazing season during 3 summers from 1992-1994. Grazing was initiated in mid-May and terminated the last week of September or the f irst week of October each year. At the end of each grazing season forage sa mples were clipped inside and outside of cages randomly located in each pas ture to estimate end of season standing crop and forage utilization. Animal activity data were collected for 9 days during August and September 1994. Steer weight gains were not different among crested wheatgrass, western whe atgrass, smooth bromegrass and flat native pastures, but weight gains of st eers grazing rolling native pastures were lower (P<0.05) than gains on othe r pastures. Weight gains per steer were 8% higher (P<0.05) on moderately gr azed pastures, but weight gains per hectare were 39% higher on heavy grazed pastures. Steers spent more (P<0.05) time grazing on smooth bromegrass tha n western wheatgrass, crested wheatgrass, or fiat native pastures and they also spent more (P<0.05) time grazing on heavy than moderately grazed pastu res. Seeded cool-season grasses produced season-long yearling steer weight gains comparable to flat native, and superior to rolling native pastures, e ven when grazed at a stocking rate that was 80% heavier than the rate recom mended for native rangeland by the USDA-SCS (1984). These results suggest t hat seeded coot-season grasses can be successfully grazed season-long in th e Northern Great plains where environmental conditions and precipitation pa tterns are comparable to central North Dakota.