Foraging ecology & management of beef cattle wintering in the central Rocky Mountains

Abstract

Winter is the most challenging period to manage livestock grazing. Unpredictable environmental extremes bring severe cold, snow, and wind. The nutritional content of forage is low and can be difficult to access due to drifting snow. Providing livestock with a supplement is the most commonly recommended strategy for dealing with these challenges, however, the success of supplementation is based upon a series of poorly understood factors. While it is broadly understood that forage is low-quality during the winter, the exact nutritional content and the variation thereof are poorly understood. Further, understanding the way livestock interact with the forage and the landscape has not been well developed, either independently, or in response to supplementation. Therefore, to bring clarity to these problems, we established two lines of research at Montana State University's Red Bluff Research Ranch in Norris, Montana. First, we evaluated the winter temporal variation in forage quality and the environmental changes associated with it. Second, we completed three subsequent two-year studies evaluating the foraging behavior and resource use of beef cattle throughout the winter in response to various protein supplementation treatments. Over two years of biweekly sampling the forage quality of the top two graminoids at Red Bluff, we detected dynamic, at times rapid shifts in crude protein (1.9-4.0%) and acid detergent fiber (37-42%) associated with changes in temperature. Using a circular moving window, vegetation and topography covariates were scaled between 30 m and 2550 m. Over the course of all six years, patch-level (30 m) cattle resource use patterns were most strongly explained by intermediate (570-1650 m) and coarse (2370-2550 m) scale covariates. When provided on alternate days, the act of providing a protein supplement shifted cattle behavior immediately afterward but otherwise the effects on activity were minimal. When evaluating the amount provided, protein supplementation decreases the intensity and duration of foraging activity, expands the total area used, and increases the use of areas at higher elevations and further from water. Overall, our research provides insight into the complex interplay between the spatial and temporal dimensions of forage quality and cattle foraging behavior.