Animal Industry Report

Extension Number

ASL R2691



Summary and Implications

The effects of stocking densities of fall-calving Angus cattle grazing cool-season pastures on cow and calf performance; forage mass, quality, and botanical composition; soil carbon content and compaction; and grazing selectivity of cattle were evaluated. Two blocks of three 10-acre cool-season pastures, divided into 1-acre paddocks, were grazed by 10 fall-calving Angus cows by one of three stocking systems: rotational stocking (RS, low stocking density), strip stocking (SS, moderate stocking density), and mob stocking (MS, high stocking density). Pastures were grazed from mid-May through late September in 2010 (yr 1) and 2011 (yr 2). Cattle received a daily live forage dry matter (DM) allowance of 4.0 and 3.2% of cow body weight (BW) in yr 1 and 2, respectively. Cattle in RS pastures were moved to new paddocks after initial forage sward height, measured with a falling plate meter (8.8 lb/yd2), was reduced by 50% by measurement (yr 1), and after the estimated intake at 3.2% of cow BW/day (yr 2). Cattle in SS and MS pastures received strips containing 100 and 25% of the daily forage allowance one and four times per day, respectively. Cow BCS did not differ between treatments in any month of either year. Cow BW was greater in MS than RS and SS pastures in June of yr 2 and greater in RS than MS pastures in August of yr 2, but did not differ in any other months of either year. Birth weight and average daily gain (ADG) of live calves at the end of the trial did not differ between treatments in either year; however, there were fewer calves per cow in MS pastures at the termination of the trial in yr 2. Forage sward height did not differ between treatments in any month of either year. Rotational stocking decreased forage disappearance in yr 2 compared to strip or mob stocking. Forage disappearance was lower in RS than SS and MS pastures in May and June of both years and was greater in RS than SS pastures in September of yr 1, but did not differ in any other months. Forage botanical composition prior to grazing each year did not differ between years, but dead forage as a percent of total forage DM was lower in RS than SS and MS pastures in yr 2. Soil bulk density from 0-3 inches in yr 1, water infiltration rate into the soil in either year, and penetration resistance at depths of 0 and 3 inches in yr 2, did not differ between treatments in any month. Soil penetration resistance at 6 inches was greater in SS than RS and MS pastures in May, and was greater in MS than SS pastures in August. Grazing selectivity did not differ between treatments in yr 1. Results suggest that, at constant forage allocation, mob stocking does not affect cow or live calf performance, but may reduce the proportion of surviving calves. Mob stocking also does not affect forage mass, botanical composition, or soil compaction measures within the first two years of implementation.

Copyright Holder

Iowa State University