Stocker Grazing Performance of Annual versus Perennial Cool-season Grass System.

Livestock producers in the southern Great Plains currently rely on cool-season annual grasses for grazing.  Use of cool-season perennial grass may decrease cost of production, and improve returns to producers.  The objective of this study is to compare the performance of stocker grazing on two systems: cool-season annuals rye/ryegrass vs experimental cool-season perennial tall fescue (Festuca arundinacea Schreb. ‘AGRFA 144’) infected with a novel endophyte, (Neotyphodium coenophialum).  Paddocks of annual grass mixture [‘Oklon’ or ‘Maton II’ cereal rye (Secale cereale L.) and ‘Marshall’ ryegrass (Lolium multiflorum Lam.)] were planted in early September 2005, 2006, and 2007 whereas tall fescue was planted in late September 2005 with four replicates, followed by two additional plantings with two replicates in late September of 2006 and 2007.  Beef steers (Bos spp.) with average body weight of 245 kg were used.  Animals were weighed every 28 days of each grazing season, and stocking rates were adjusted based on forage availability.  At each grazing cycle, forage availability, forage quality, and animal performance as average daily gain (ADG) and total gain (TG) were measured.  Forage availability and quality for both grasses were high in late winter through spring and decreased thereafter.  Animals performed well in both systems with an ADG of 3.06 and 2.50 kg ha^-1 d^-1 and TG of 193 and 638 kg ha^-1 for rye/ryegrass, and ADG of 3.18 and 3.06 kg ha^-1 d^-1 and TG of 181 and 405 kg ha^-1 for tall fescue in 2005-06 and 2006-07, respectively.  The difference of TG between two systems was due to higher number of grazing days in annual system compared to the perennial system.  Considering stand life of perennial system, and reduced time, labor, and equipment requirements, tall fescue system may be profitable over time by amortizing the establishment cost.