Effects of Stocking Density On Stocker Cattle Performance, End of the Season Biomass Yield and Forage Quality of Dual Purpose Switchgrass.

Switchgrass (Panicum virgatum L.) is the primary next generation feedstock for bioenergy production. In order to justify the risk of establishing this crop during the infancy of the cellulosic bio-fuel industry, it will be important for agricultural producers to have alternative uses for switchgrass.  Stocker cattle are characterized as lightweight steers that are grown on forage prior to entry into an intensive feeding system.  A primary advantage of switchgrass as compared to other bioenergy feedstock’s is due its early spring forage potential, it can serve as a the gap filler for cattle coming off from cereal pastures and until summer pastures are ready..   Therefore, the objective of this study was to determine the effect of different stocking rates on forage yield and quality of switchgrass in a dual purpose feedstock for both grazing and biofuel. Four stocking densities; control (0 steers/ha), low (2.5 steers/ha), medium, (5 steers/ha) and high (7.5 steers/ha) were evaluated on Alamo switchgrass, a lowland ecotype that was established in 2007 on Slaughterville fine sandy loam in Oklahoma. Steer weights and forage availability were determined at the initiation and termination of grazing. The average daily gain for the high stocking treatment was 1.05 kg hd^-1 day^-1for medium it was 1.04 kg hd^-1 day^-1and for the low treatment it was 0.83 kg hd^-1 day^-1, but no significant differences were detected (P = 0.119). Stocking density also has no significant effect on total gain (P = 0.075) for the three treatments. Total gain was 199, 215 and 167 kg ha^-1 for high, medium and low stocking densities, respectively.  Grazing days were significantly affected  (P< 0.0001) by stocking density with the low stocking density paddocks enabling 81 days of grazing, the medium stocking density having 43 days of grazing and the heavy stocking allowing for 28 days of grazing. Forage biomass was collected at grazing initiation and repeated every two weeks for the first 84 days of grazing and at switchgrass physiological maturity.  Treatments did affect biomass yield at physiological maturity (P< 0.0001). Non-grazed control produced 15356 kg ha-¹ of switchgrass biomass yield.  Low stocking density produced   10550 kg ha-¹ which is two thirds of control yield where as medium and high stocking density were able to produce half of control yields with 8118 kg ha-¹ and 7778 kg ha-¹,respectively. Results from this study indicate that switchgrass can be used as a dual-use crop for stocker cattle grazing and bioenenergy feedstock.  This dual-use might provide options for producers entering the bioenergy feedstock production section, leading to a more rapid adoption of this forage.