The University of Arizona

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

J.F. Karn, R.E. Ries, L. Hofmann

Abstract


In the semi-arid Northern Great Plains, seeded cool-season grasses are primarily recommended for spring and fall grazing because their nutritive quality 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 spring stocking rates, which leave little forage remaining for mid-summer use. A study was conducted near Mandan, N.D. to determine the effect of moderate (1.6 AUM ha(-1)) and heavy (2.4 AUM ha(-1)) stocking rates on weight gains of yearling Hereford steers grazing crested wheatgrass (Agropyron desertorum [Fisch. Ex Link] Schult.), western wheatgrass (Pascopyrum smithii [Rydb.] Love), smooth bromegrass (Bromus inermis Leyss.) and flat (class II and III) and rolling (class IV and VI) native rangelands. Studies were conducted 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 first week of October each year. At the end of each grazing season forage samples were clipped inside and outside of cages randomly located in each pasture 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 wheatgrass, smooth bromegrass and flat native pastures, but weight gains of steers grazing rolling native pastures were lower (P < 0.05) than gains on other pastures. Weight gains per steer were 8% higher (P < 0.05) on moderately grazed pastures, but weight gains per hectare were 39% higher on heavy grazed pastures. Steers spent more (P < 0.05) time grazing on smooth bromegrass than western wheatgrass, crested wheatgrass, or flat native pastures and they also spent more (P < 0.05) time grazing on heavy than moderately grazed pastures. Seeded cool-season grasses produced season-long yearling steer weight gains comparable to flat native, and superior to rolling native pastures, even when grazed at a stocking rate that was 80% heavier than the rate recommended for native rangeland by the USDA-SCS (1984). These results suggest that seeded cool-season grasses can be successfully grazed season-long in the Northern Great Plains where environmental conditions and precipitation patterns are comparable to central North Dakota.

Keywords


native grasslands;physical activity;Bromus inermis;sown grasslands;Agropyron desertorum;liveweight gain;duration;stocking rate;steers;Pascopyrum smithii;grazing intensity;rangelands;grazing;North Dakota

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