Integrated Warm- and Cool-Season Grass and Legume Pastures. I. Seasonal Forage Dynamics

High temperatures and scarce precipitation often cause the productivity and quality of cool-season pastures in Southwest Michigan to decline for an extended period during the summer. This study was conducted to determine whether integration of switchgrass (Panicum virgatum L.) or big bluestem (Andropogon gerardii Vitm.) into cool-season grazing systems would mitigate this period of low pasture productivity and quality. Cool-season grass and legume pastures (CS-Only) were compared to integrated big bluestem and cool-season grass and legume pastures (CS-BBS) and integrated switchgrass and cool-season grass and legume pastures (CS-SG). The seasonal dynamics of forage dry matter offered, crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) were used to compare the dynamics of the pasture productivity and quality in each of three treatments. Dry matter offered in the CS-Only treatment was higher earlier in the grazing season and the peak in dry matter-offered occurred between 20 and 30 d earlier in the CS-Only treatment than in the other treatments. The seasonal trend for CP was generally higher and more constant for the CS-Only treatment than for the CS-BBS and CS-SG treatments, which were very similar to each other. The seasonal trend for ADF and NDF was generally lower and more constant for the CS-Only treatment than for the CS-BBS and CS-SG treatments, which were very similar to each other. These findings suggest that, compared to the CS-Only treatment, the CS-SG or the CS-BBS treatments probably will not improve livestock gain or improve the distribution of animal grazing days throughout the summer.