Grazing Intensities, Vegetation, and Heifer Gains: 55 Years on Shortgrass

Abstract

Shortgrass rangeland, dominated by blue grama (Bouteloua gracilis [H.B.K.] Lag. ex Steud), was grazed at 3 intensities, equivalent to mean stocking rates of 16.7, 23.0, and 36.5 beiferdays ha-', from 1939 through 1994. Few changes in plant communities had been documented by the early 1970's. In 1992-1994, frequency of occurrence, basal and foliar cover, and biomass at peak standing crop (PSC) were determined on the remaining pasture at each grazing intensity, and on 3 ungrazed exclosures. Blue grama and buffalograss (Buchloif dactyloides [Nutt.] Engelm.) increased, and western wheatgrass (Puwopyrum smithii [Rydb.] A. Love) and needle-and-thread (Spa coma&z Trin. & Rupr.) decreased, as grazing intensity increased. Redthree-awn (Aristiah longisetu Steud.) was most plentiful under light grazing. Basal cover and biomass of forbs were lower under grazing than in exclosures, but differences in biomass were not significant. Shrubs and half-shrubs decreased as grazing intensity increased. Frequency and cover of plains pricklypear (Opuntia polyacantha Haw.) were higher in the exclosures and under fight grazing than under moderate or heavy grazing; biomass was 4 to 6 times as high in the exclosures as under any grazing intensity, Heifer gains declined linearly with increasing grazing pressure index. Optimum (most profitable) stocking rate was about 20% higher than that under the moderate grazing intensity, under which biomass production was maintained and shrub and pricklypear remained at low levels. Returns to land, labor, and management were only slightly higher under the optimum stocking rate than under the moderate grazing intensity. The moderate grazing intensity appears to be both profitable and sustainable.

Effect of cattle grazing a species-rich mountain pasture under different stocking rates on the dynamics of diet selection and sward structure

“…This has been confirmed by surveys of changes in the botanical composition of pastures following a reduction of management intensity or stocking rates (e.g. Kiehl et al, 1996;Hart and Ashby, 1998;Marriott et al, 2004). However, a very low stocking rate is also assumed to reduce plant diversity as a result of competitive exclusion, where the high productivity of some species dominates plant species that cannot compete for light (Grime, 1979).…”

“…Although a number of studies have measured the impact of cattle on permanent pastures grazed at different stocking rates (e.g. Hart and Ashby, 1998;Orr et al, 2001;Gillen and Sims, 2006), only a few analysed seasonal patterns in pasture use (Ash and McIvor, 1998;Kohler et al, 2006) and simultaneously quantified the dietary choices of the animals (Mayer et al, 2003). Yet, many features of the structural heterogeneity of swards are the result of decisions made by grazing herbivores about where and when to place bites (Parsons and Dumont, 2003).…”

Temperature and Precipitation Affect Steer Weight Gains Differentially by Stocking Rate in Northern Mixed-Grass Prairie

“…There are few long-term studies undertaken in resource management (Lindenmayer et al 2012) and beef production (Briske et al 2011), although such studies are invaluable. Of the few studies that have addressed long-term cattle weight gains (e.g., Willms et al 1986;Hart and Ashby 1998;Derner et al 2008), only Derner et al (2008) examined the influence of precipitation on cattle weight gains, finding that higher spring (April-June) precipitation totals increased beef production in northern mixed-grass prairie. Further elucidating the effects of precipitation (and temperature) on beef production would assist in modeling efforts to help ranchers maximize production and minimize enterprise risk (Derner et al 2012).…”

Journal of Range Management, Volume 55, Number 5 (September 2002)

“…These include a short stature (Bouteloua gracilis and Buchloe dactyloides), a sprawling habit (Schedonnardus paniculatus), and sharptipped awns (Aristida purpurea). Buchloe dactyloides has also been shown to be very tolerant of high rates of cattle herbivory (Klipple and Costello 1960, Launchbaugh 1967, Hart and Ashby 1998 …”