Vegetation and livestock response to increasing stocking rates in a simulated short-duration grazing system

Abstract

A short-duration grazing (SDG) system was simulated to evaluate the vegetation and livestock response to stocking rates ranging from the recommended to 2.67 times the recommended rate for moderate continuous grazing. Precipitation was 30% above average and evenly distributed throughout the year. All forage classes responded favorably to the above average precipitation except mid-grasses. Heavy utilization in the 51 day grazing cycles restricted mid-grass standing crop in all stocking rates. Common curlymesquite (Hilaria belangeri) was particularly responsive to the favorable precipitations in the two lighter stocking rates and on the better sites. Stocking rates greater than 1.5 times the recommended rate significantly reduced total herbaceous standing crop. However, above-ground net primary production (ANPP) was maintained during this year of above average precipitation. Livestock consumed 49% of ANPP in the heaviest stocking rate compared to only 22% in the lightest rate. This reflects the potential of SDG to generate high grazing pressures to greatly increase the proportion of forage harvested by livestock. Diet quality declined during the cool season as grazing pressure on live green forage increased. Sheep switched from forbs and cool-season grass to dormant warm-season grass, and cattle switched from cool-season grass and forbs to sacahuista (Nolina texana) and prickypear (Opuntia macrorhiza) with a resulting decline in diet quality. The high standing crop in the growing season reduced the grazing pressure in all treatments and resulted in no significant differences in diet quality.