|Hart, Richard - RETIRED ARS|
Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: August 25, 2007
Publication Date: January 26, 2008
Citation: Derner, J.D., Hart, R.H. 2008. Reductions in livestock gain with rotational grazing and heavy stocking rates in northern mixed-grass prairie. In: Proceedings of the Annual American Forage and Grassland Council and Society for Range Management mtngs "Building bridges: Grasslands to rangelands." Louisville, KY, January 2008. CDROM, Abstract #1724. Technical Abstract: The effects of stocking rate and grazing system on gains of yearling beef cattle grazing rangelands have largely been addressed in short-term (<10 yr) studies, and often stocking rates are confounded within grazing systems with higher stocking rates for short-duration rotational grazing systems compared to season-long grazing. A grazing system (season-long and short-duration rotational grazing) X stocking rate (light: 1.30 ha/steer/month, moderate: 0.63 ha/steer/month, and heavy: 0.46 ha/steer/month) study was initiated in 1982 on northern mixed-grass prairie. Here, we report on the final 16 years (1991-2006) for yearling beef cattle gains. Average daily gains (kg/head/day) across all years with season-long grazing decreased with increasing stocking rate and grazing pressure. Heavy stocking rates reduced average daily gain by 16% and 12% compared to light and moderate stocking rates, respectively. In contrast to average daily gain, beef production (kg/ha) increased with increasing stocking rate and grazing pressure. Cattle gains were reduced by 6% with short-duration rotation compared to season-long grazing over the study period, with differences between systems observed in years with average, but not dry or wet, spring (April+May+June) precipitation. Grazing season gains (kg/head) and beef production both exhibited significant increasing hyperbolic relationships with spring precipitation, with the percentage of variation explained by spring precipitation substantially higher (62-83%) for beef production compared to grazing season gains (32-45%). The influence of spring precipitation on cattle gains suggests that incorporation of these relationships into modeling efforts for strategic planning and risk assessment will assist land managers in better matching forage and animal resources for greater sustainability in this highly variable environment.