Evaluation of switchgrass and big bluestem for use in cool-season grazing systems to improve seasonal forage yield and livestock gains

Michigan livestock producers are faced with a choice that arises annually: to move their livestock from dormant summer pastures to locations where they are fed stored forage, or to allow their livestock to continue grazing, risking damage to the land. Keeping livestock on high-quality pasture is in the economic interest of the farmer, the physical interest of the animal, and the land itself. In this study we compared a typical Michigan grazing system with two other grazing systems, each of which integrate one native warm season grass species into the typical grazing system to provide quality midsummer forage. The grazing experiment was conducted at the W.K. Kellogg Biological Station in Hickory Corners, MI. A completely randomized design with four replications was used. Treatments for this trial include: (1) traditional Michigan cool season grass/legume pasture; (2) a treatment two-thirds of which is the same as '1)' and one-third of which is composed of switchgrass (Panicum virgatum); (3) a treatment two-thirds of which the same as to '1)' and one-third which is composed of big bluestem (Andropogon gerardii). A variable stocking rate was be used and pastures were rotationally grazed. Grazing began in late-April and ended by October 15 of each year, depending upon conditions. Pasture performance is described in terms of forage dry matter offered throughout the grazing season, botanical composition, forage quality, number and distribution of animal unit grazing days, average daily gain of animals on pasture, and total animal weight gain/hectare. The animals used in this study were Holstein steers, weighing approximately 240 kg at the beginning of the grazing season. Results reveal that although average daily gains do not differ among treatments, total animal weight gain per hectare is significantly different among treatments. Inclusion of big bluestem or switchgrass in a grazing system may reduce the risk of extreme declines in available pasture dry matter, but management constraints of these grasses reduce total grazable acreage in the spring and early fall. Economic comparisons that include variable costs show that integrating switchgrass or big bluestem into traditional cool-season grass and legume pastures in the proportions used in this experiment will result in an economic disadvantage for southwest Lower Michigan livestock producers. However, these differences in economic performance could be offset by moderate financial incentives from organizations that wish to encourage livestock producers to enhance wildlife habitat by including switchgrass and big bluestem in their grazing systems. There were no significant differences in the relative abundance of grassland birds among the treatments. The size and design of the grazing experiment was not suitable for rigorous research on the effect of native warm season grasses in grazing systems on grassland bird species.