Grazing effects on nutritional quality of bluebunch wheat-grass for elk

Abstract

We tested the hypothesis that nutrient content of bluebunch wheatgrass (Agropyron spicatum [Pursh] Scribn. &Smith) either cattle grazed in the spring, rested from cattle grazing for a full year, or given long term rest would all be equal during the given season at 1 location. A 3 pasture rest-rotation grazing system and an exclosure on the Mt. Fleece elk winter range in southwestern Montana were studied during 4 seasons over 3 years. Only nitrogen (N) and phosphorus contents were generally greater in the in the spring grazed regrowth pasture. However, regrowth from bluebunch wheatgrass grazed in the spring did not improve the species nutrient content for wildlife the following winter over nongrazed treatments. During winter when elk (Cervus elaphus nelsoni Bailey) are present, N, TDN, and IVDMD were not among the 3 treatments. Elk were determined unlikely to consume enough bluebunch wheatgrass to meet protein maintenance requirements during winter. Our findings resulted from analyses repeated over the 3 years for a complete cycle of a 3 pasture rest-rotation system: however, our hypothesis needs to be tested at other locations before assuming the same results elsewhere.