Utilization of Switchgrass in a Dual Purpose Stocker Cattle and Bioenergy System.

The objective of this study was to determine if switchgrass (Panicum virgatum) produced for bioenergy production could serve as a dual crop in stocker cattle management programs.  Switchgrass is a native grass that produces sufficient biomass on marginal lands to serve as a bio-refinery feedstock.  Stocker cattle production generally involves lightweight calves developed on forage-based diets for feedlot production or cow replacements.  In May 2007, 9.7 ha of switchgrass (cultivar Alamo) was established in southern Oklahoma on sandy soil and divided into twelve, 0.8 ha paddocks to evaluate stocker cattle performance and switchgrass utilization at 4 stocking densities.  In April 2008, steers (n = 36) weighing 348 kg, were randomly assigned to control (0 steers/ha), low (2.5 steers/ha), medium, (5 steers/ha) and high (7.5 steers/ha) stocking density paddocks.  Herbage mass and nutrient composition were measured bi-weekly during the grazing period and at completion of switchgrass growing season (September).  Animal weights were collected on d 0 and at completion of grazing.  Grazing was terminated when forage height was less than 10 cm.  Overall, ADG and total gain per ha was not significantly affected (P = .34) by treatment but a numerical trend was observed with the higher stocking density (1.5 kg/d) outperforming both the low (0.8 kg/d) and medium (1.2 kg/d) stocking densities.  Stocking density significantly affected (P<.001) total grazing days with the high density (21d) resulting in fewer days than either low (98d) or medium (30d) stocking densities.  Stocking density did not affect (P>.05) biomass availability at conclusion of growing season, however grazing significantly (P<.01) reduced overall biomass.  Control paddocks contained 14,100 kg/ha at conclusion of growing season, whereas grazed paddocks averaged 7,615 kg/ha.  Nutrient composition was not significantly affected by grazing (P<.05).  While grazing reduced biomass availability of switchgrass, the significant animal performance gained could impact producer profitability.