Animal Industry Report

Extension Number

ASL R2613



Summary and Implications

Cattle congregating near pasture streams decrease forage sward height and root mass and increase fecal cover, 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 amount of time cattle spend near or in the stream, in turn reducing the risks of water quality impairment. However, the effectiveness of these management practices may be affected by pasture size. Six 30-acre cool-season grass pastures on the Rhodes Research Farm bisected by a 46375-ft stream reach 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 cattle 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 stream access to 16-ft wide stabilized crossings (CSR) were compared in pastures with two sizes (10 and 30 acres) in an experiment with a 3 x 2 switchback design with 2 week periods over 5 monthly intervals. Five and fifteen fall-calving Angus cows (mean initial weight, 1305 lbs) were continuously stocked in each small and large pasture, respectively. At the beginning of each period, 2 or 3 cows per pasture were fitted with GPS collars that recorded cow position every 10 minutes for the two week period. Pasture size had little effect on the proportion of time that cows in pastures with restricted stream access were in the stream until the fourth (August 17 to September 14) and fifth (September 14 to October 12) interval. However, cows in pastures with unrestricted stream access with or without off-stream water spent more (P<0.05) time in Streamside Zones (between 15 and 110 feet of the stream) in small pastures than large pastures. Cows with restricted stream access spent less (P<0.05) time in the Stream (0 to 15 feet from the stream) and Streamside Zones than cows in pastures with unrestricted stream access regardless of pasture size. Off-stream water had little effect on the amount of time cattle spent in or near pasture streams regardless of pasture size.

Copyright Holder

Iowa State University