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Animal Industry Report

Extension Number

ASL R2585

Topic

Beef

Summary and Implications

Fall-calving Angus cows grazed tall fescue pastures by three stocking systems to determine their effects on forage yield, quality, and species composition; soil carbon content, bulk density, and water infiltration; and cow and calf performance. In May 2010, two blocks of three 10-acre tall fescue pastures were each subdivided into ten 1-acre paddocks. Sixty cows (mean bodyweight 1291 lb and body condition score (BCS) 4.84 on a 9-point scale) were randomly allotted to the six pastures. One of three stocking systems was randomly assigned to one of the pastures within each block: rotational (RS), strip (SS), or mob (MS) stocking. Grazing of pastures in the RS, SS, and MS treatments was initiated on May 14, 14, and 26 respectively, and continued until September 30. Cows in RS pastures were moved to a new paddock daily for the first 21 days. Cows in the RS pastures after the first 21 days, and cows in the SS and MS treatments throughout the grazing season, were provided live forage DM at an allowance of 4% BW/day except from August 1 through mid September, when allocation was increased to 5% BW/day to account for the increased demands of lactation. Residency time or strip size was determined by measuring forage DM with a falling plate meter (8.8 lb/yd2) before and after cows were rotated into a new paddock. Cows in RS pastures were moved to a new paddock when 50% of the live forage DM was consumed. Paddocks in SS pastures were subdivided into strips providing the assigned daily forage allowance and cows were given access to a new strip daily with no backfence installed. Paddocks in the MS pastures were subdivided into strips to provide 25% of the assigned daily forage allowance and cows were moved into new strips with a backfence installed four times daily. Mineral and water were provided ad libitum. Cow BW did not differ between treatments in any month. Cow BCS was lower for cows in the SS pastures than RS or MS pastures at the initiation of grazing in May. BCS of cows in RS pastures were greater (P < 0.05) than SS or MS pastures in August. The proportion of calved cows, live births, and calves alive at the termination of grazing, and the calf birth weight and average daily gain (ADG) did not differ between treatments. Average pasture sward height was lower (P < 0.05) in RS than SS and MS pastures in June, but did not differ in other months. Grazing efficiency, as measured with the falling plate meter, was lower (P < 0.05) in RS than SS or MS pastures in May, but did not differ in other months. Water infiltration rates into the soil and soil moisture content measured in May, July, and October did not differ between blocks or treatments. Ongoing analysis will allow more complete comparisons in the future.

Copyright Holder

Iowa State University

Language

en

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