Effects of Grazing Pressure on Efficiency of Grazing on North American Great Plains Rangelands

• Published in: Rangeland ecology & management Vol. 63; no. 4; pp. 397 - 406
• Main Authors: Smart, A. J., Derner, J. D., Hendrickson, J. R., Gillen, R. L., Dunn, B. H., Mousel, E. M., Johnson, P. S., Gates, R. N., Sedivec, K. K., Harmoney, K. R., Volesky, J. D., Olson, K. C.
• Format: Journal Article
• Language: English
• Published: Rangeland Ecology & Management, P.O. Box 7065, Lawrence, KS 66044 Society for Range Management 01-07-2010; Elsevier Inc; Allen Press Publishing Services; Elsevier Limited
• Subjects: animal performance; animal production; Animals; Cattle; Decision making; dry matter accumulation; Efficiency; equations; Forage; forage disappearance; foraging; Forum; Grazing; grazing efficiency; grazing intensity; Grazing management; grazing pressure index; harvest efficiency; harvest efficiency value; herbage intake; insect pests; Light; Livestock; liveweight gain; Management decisions; meta-analysis; Methods; nonlivestock forage losses; Pastures; prediction; Range management; rangelands; senescence; Stock market indices; Stocking rate; Studies; utilization; Vegetation; weathering; wildlife; yields; Wyoming; Colorado; Oklahoma; Great Plains region; South Dakota; Kansas; North Dakota; animal performance; grazing efficiency; forage disappearance; harvest efficiency; herbage intake; utilization; stocking rate
• ISSN: 1550-7424; 1551-5028; 1551-5028
• DOI: 10.2111/REM-D-09-00046.1

Comparisons of stocking rates across sites can be facilitated by calculating grazing pressure. We used peak standing crop and stocking rates from six studies in the North American Great Plains (Cheyenne, Wyoming; Cottonwood, South Dakota; Hays, Kansas; Nunn, Colorado; Streeter, North Dakota; and Woodward, Oklahoma) to calculate a grazing pressure index and develop relationships for harvest efficiency, utilization, grazing efficiency, and animal performance and production. Average grazing pressures for heavy, moderate, and light stocking across the study sites were 40, 24, and 14 animal unit days · Mg−1, respectively. These grazing pressures resulted in average harvest efficiency values of 38%, 24%, and 14% and grazing efficiencies of 61%, 49%, and 39% for heavy, moderate, and light stocking rates, respectively. Utilization increased quadratically as grazing pressure index increased, whereas grazing and harvest efficiencies exhibited a linear increase with grazing pressure. The latter indicates that nonlivestock forage losses (e.g., weathering, senescence, wildlife, insects) were disproportional across stocking rates. Average daily gain of livestock decreased linearly as grazing pressure index increased across study sites. Prediction equations reaffirm assumptions of 50% grazing efficiency and 25% harvest efficiency associated with moderate stocking. Novel here, however, is that harvest and grazing efficiencies increased at high grazing pressures and decreased at low grazing pressures. Use of grazing pressure index to “standardize” stocking rates across rangeland ecosystems in the North American Great Plains should improve communication among scientists, resource managers, and the public, and thus better achieve both production and conservation goals on these lands.