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Animal Industry Report

Extension Number

ASL R2323

Topic

Environment

Summary and Implications

Grazing management may alter the characteristics of a pasture sward that affect both the nutritional value of the forage and the environmental impacts of the grazing system. Six 30-acre cool-season grass pastures, containing predominantly smooth bromegrass and bisected by a 642- foot stream segment, were grouped into 2 blocks and assigned one of three treatments: continuous stocking - unrestricted stream access (CSU), continuous stocking - restricted stream access (CSR), and rotational stocking (RS). Forage sward height and mass and the proportions of bare or fecal-covered ground were determined monthly from open and congregation areas within 4 zones in the pasture. Zones were defined as on the stream bank (bank), from the stream bank to 110 feet from the stream bank (110), 110 feet to 220 feet from the stream bank (220), and greater than 220 feet from the stream bank (upland). Forage samples were analyzed for in vitro dry matter disappearance (IVDMD), crude protein (CP), and phosphorus (P). Bare ground and fecal cover were greater and forage mass was lower in congregation than in open areas of pastures. Proportion of bare ground along stream banks did not significantly differ (P>.10) between grazing management treatments in most months. However, the proportions of bare ground within 110 feet of the stream in pastures with the CSU treatment were greater than the CSR or RS pastures in late summer of 2005 and 2006. Proportions of fecal-covered ground on stream banks in pastures with the CSU treatment were greater than CSR and RS pastures in mid-summer of each year. Forage masses within 110 feet of the stream in pastures with the CSR treatment were greater than the CSU pastures in late summer of each year. However, proportions of bare ground and forage mass did not differ between grazing management treatments throughout the portions of the pastures available for grazing. In Vitro dry matter disappearance and concentrations of CP and P in available forage did not differ between grazing treatments in any month.

Copyright Holder

Iowa State University

Language

en

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