Pasture size effects on the ability of off-stream water or restricted stream access to alter the spatial/temporal distribution of grazing beef cows1,2,3

Abstract

For 2 grazing seasons, effects of pasture size, stream access, and off-stream water on cow distribution relative to a stream were evaluated in six 12.1-ha cool-season grass pastures. Two pasture sizes (small [4.0 ha] and large [12.1 ha]) with 3 management treatments (unrestricted stream access without off-stream water [U], unrestricted stream access with off-stream water [UW], and stream access restricted to a stabilized stream crossing [R]) were alternated between pasture sizes every 2 wk for 5 consecutive 4-wk intervals in each grazing season. Small and large pastures were stocked with 5 and 15 August-calving cows from mid May through mid October. At 10-min intervals, cow location was determined with Global Positioning System collars fitted on 2 to 3 cows in each pasture and identified when observed in the stream (0-10 m from the stream) or riparian (0-33 m from the stream) zones and ambient temperature was recorded with on-site weather stations. Over all intervals, cows were observed more (P ≤ 0.01) frequently in the stream and riparian zones of small than large pastures regardless of management treatment. Cows in R pastures had 24 and 8% less (P < 0.01) observations in the stream and riparian zones than U or UW pastures regardless of pasture size. Off-stream water had little effect on the presence of cows in or near pasture streams regardless of pasture size. In 2011, the probability of cow presence in the stream and riparian zones increased at greater (P < 0.04) rates as ambient temperature increased in U and UW pastures than in 2010. As ambient temperature increased, the probability of cow presence in the stream and riparian zones increased at greater (P < 0.01) rates in small than large pastures. Across pasture sizes, the probability of cow presence in the stream and riparian zone increased less (P < 0.01) with increasing ambient temperatures in R than U and UW pastures. Rates of increase in the probability of cow presence in shade (within 10 m of tree drip lines) in the total pasture with increasing temperatures did not differ between treatments. However, probability of cow presence in riparian shade increased at greater (P < 0.01) rates in small than large pastures. Pasture size was a major factor affecting congregation of cows in or near pasture streams with unrestricted access.

FORAGES AND PASTURES SYMPOSIUM: Improving soil health and productivity on grasslands using managed grazing of livestock1

“…In comparison with land used for row crop production, the perennial vegetation provided by grasslands will increase SOC content and water infiltration while reducing soil bulk density (Tiessen et al, 1994;Franzluebbers, 2002;Follett and Reed, 2010). With appropriate management of stocking rate and system for the plant species and soil conditions within a grassland ecosystem, plant community diversity (Hickman et al, 2004;Volesky et al, 2004;Guretzky et al, 2005), SOC content (Schuman et al, 2002;Conant et al, 2003;Franzluebbers and Stuedemann, 2009), and wildlife habitat (Fuhlendorf and Engle, 2001;Tews et al, 2004;Bisinger et al, 2014) of grasslands may be improved by grazing. Furthermore, whereas grazing may increase soil bulk density, water infiltration rate can be sustained by grazing management practices that maintain adequate ground cover.…”

“…But assuming a hoof contact area of 100 cm 2 (Scholefield et al, 1985), a distance walked per cow of 4.05 km/d in a 12.1-ha coolseason pasture (Davis et al, 2011), and a number of steps walked per kilometer of 995 by grazing cows calculated from Aharoni et al (2009), each unit of land in a 12.1-ha cool-season pasture stocked with 15 cows would have been trodden 2.8 times over a 140-d grazing season if cattle were evenly distributed. As 10.1% of observations of cows grazing in 12.1-ha pastures were within 33 m of a stream bisecting the pastures, which represented 7.2% of pasture area (Haan et al, 2010;Bisinger et al, 2014), each unit of land within this ecologically sensitive area would have been trodden 3.9 times over a 140-d grazing season if cattle had unrestricted access to the stream. Furthermore, as the proportion of observations within 33 m of a stream increased to 28.2% when the pasture size was reduced from 12.1 to 4.04 ha (Bisinger et al, 2014), each unit of land within 33 m of the stream of a 4.04-ha pasture would have been trodden as many as 10.8 times over a 140-d grazing season, if the stocking rate was proportional in the smaller pasture.…”

“…As 10.1% of observations of cows grazing in 12.1-ha pastures were within 33 m of a stream bisecting the pastures, which represented 7.2% of pasture area (Haan et al, 2010;Bisinger et al, 2014), each unit of land within this ecologically sensitive area would have been trodden 3.9 times over a 140-d grazing season if cattle had unrestricted access to the stream. Furthermore, as the proportion of observations within 33 m of a stream increased to 28.2% when the pasture size was reduced from 12.1 to 4.04 ha (Bisinger et al, 2014), each unit of land within 33 m of the stream of a 4.04-ha pasture would have been trodden as many as 10.8 times over a 140-d grazing season, if the stocking rate was proportional in the smaller pasture. In addition to compaction resulting from vertical compression, smearing of the soil surface and tearing of vegetation may be caused by the tangential force exerted horizontally by the hooves of a walking animal (Bilotta et al, 2007).…”

“…The timing and level of disturbance from strategically managed grazing has the potential to influence plant community composition and available habitat for wildlife species (Fuhlendorf and Engle, 2001;Tews et al, 2004;Bisinger et al, 2014). For example, whereas high-density, short-duration stocking decreased the proportion of cool-season grass species, it increased the proportion of annual grass and legume species (Bisinger, 2014).…”

How does pasture size alter plant–herbivore interactions among grazing cattle?

“…This large pasture, which had a single water source located at one end, was deliberately designed to produce a gradient of cattle distribution. The second study, which was by Bisinger et al (2014), focused on three management options to modify stream access by calving cows in 4-ha versus 12-ha pastures.…”