Animal Industry Report

Extension Number

ASL R2692



Summary and Implications

Cattle congregating near pasture streams decrease forage sward height and root mass and increase fecal cover, thereby, increasing the risk of sediment, nutrient, and pathogen loading of the streams. Restricting stream access to stabilized crossings or offering off-stream water may decrease the time cattle spend near or in pasture streams, in turn reducing the risk of water quality impairment. However, the effectiveness of these management practices may be affected by pasture size. In a two-year study, six 30- acre cool-season grass pastures bisected by a 475-ft stream reach on the Rhodes Research Farm were used to analyze the effects of pasture size on the efficacy of restricted stream access or off-stream water to alter the spatial/ temporal distribution of grazing cows in and near the pasture stream. Three grazing management treatments: unrestricted stream access without off-stream water (CSU), unrestricted stream access with off-stream water (CSUW), and restricted access to 16-ft wide stabilized crossings (CSR) were compared in two pasture sizes (10 and 30 acres) in five 4-week intervals with 2-week periods between May 18 and October 12 in 2010 and May 18 to October 8 in 2011. Five and fifteen fall-calving Angus cows were continuously stocked in each small and large pasture, respectively. At the beginning of each period two to three cows were fitted with GPS collars that recorded cow position every 10 minutes. Cows in small pastures with unrestricted stream access with or without off-stream water spent more (P<0.05) time in stream (0 to 16 feet from stream) and streamside (16 to 118 feet from stream) zones in small treatments than large treatments. Restricting stream access to stabilized stream crossings reduced the time cows spent in the stream and streamside zones compared to unrestricted stream access in small and large treatments. Regardless of pasture size, off-stream water had little effect on cow presence in the stream zone.

Copyright Holder

Iowa State University