Effect of Grazing System on Livestock Performance, Botanical Composition, and Standing Crop in the Nebraska Sandhills

Authors

Mitchell B. Stephenson, University of Nebraska - LincolnFollow

Date of this Version

5-2010

Comments

A Thesis presented to the faculty of the graduate college at the University of Nebraska in partial fulfillment of requirements for the degree of master of science Lincoln, Nebraska May, 2010 Copyright 2010. Mitchell Stephenson

Abstract

A 10-year study compared a 4-pasture deferred-rotation (DR) grazing system with an 8-pasture short duration grazing (SDG) system at the Barta Brothers Ranch near Rose, NE to determine differences in livestock performance, botanical composition, and standing crop. Pastures were grazed by 50 to100 cow-calf pairs with both single (DR system) and multiple (SDG system) grazing periods from 15 May to 15 October. Livestock performance data were collected from spayed heifers substituted into each grazing system during the last 3 years of the study. Botanical composition was collected on 275 frequency of occurrence transects in 1998, 2003, and 2008. Standing crop data were collected biannually within 240 grazing exclosures placed at 4 topographic positions from 2000 to 2008. Average daily gain of the spayed heifers (0.84 kg∙day-1) did not differ between grazing systems and years. The DR grazing system had minimal increases of standing crop and frequency of occurrence of desirable plant species. Standing crop and frequency of occurrence were more affected by topographic position and year than by grazing system treatments. Effect of timing of grazing on subsequent-year standing crop was also determined with the DR and SDG grazing systems. Standing crop data were used to determine effect of time of grazing on plant functional groups. Subsequent-year warm-season grass standing crop with the DR system was lowest when grazing occurred from 21 July to 31 August. Cool- season grass and forb standing crop was most affected when grazing took place in mid-May, mid-June, and late-August within the SDG system Browse production tended to be lower when grazing occurred early in the grazing season for both grazing systems. Grazing during times when standing crop is most limited in subsequent-years should not take place in consecutive years on pastures in either system unless specific management objectives are trying to be obtained.