Abstract.  Management-intensive rotational grazing (MIRG) is used by many farmers seeking to balance profitability and environmental stewardship.  Productivity of pastures in much of the upper Midwest is limited to April through October, so promoting high quality forage production for summer grazing and winter storage is critical to dairy and beef farm profitability.  We conducted a field experiment on pastures dominated by Kentucky bluegrass, orchardgrass, perennial ryegrass, and red clover to compare forage production under MIRG and continuous grazing (CONT).  Grazing treatments were established in May 2005 in a randomized complete block design with 3 blocks at the Franbrook Farm, a University of Wisconsin-Madison research farm.  MIRG paddocks were stocked with cow-calf pairs at high density (41 AU/ha) for 2 d and then allowed to rest for 28 d.  CONT pastures had lower stocking densities (3 AU/ha) and pastures were rested for only 2 d per month.  Fifty-seven kg N/ha of granular ammonium nitrate was applied fall 2005 and again in fall 2006.  Total forage production for the 2005 growing season was not significantly different between MIRG and CONT treatments, but by summer 2006, it was apparent that much of the biomass in the CONT pastures was being refused by livestock.  Total forage production for 2006 was 10,653 kg/ha, and 8,820 kg/ha for MIRG and CONT, respectively.  We incorporated estimates of refused biomass from both treatments into our 2006 forage production calculations and found the gap between total un-refused forage in MIRG and CONT increased (10,546 kg/ha and 6,703 kg/ha, respectively).  Biomass from both treatments was sampled over the growing season and analyzed using Near Infrared Reflectance Spectroscopy (NIRS).  Relative Forage Quality (RFQ) of biomass harvested from the MIRG treatments was significantly greater than biomass from CONT treatments (RFQ of 149 and 112, respectively).   

Key Words: biomass, cool-season pasture, grazing, upper Midwest.