Adaptive grazing and animal density implications for stocking rate and drought in northern mixed-grass prairie

Temporal variability drives soil chemical and biological dynamics more than grazing in a northern mixed-grass prairie

“…However, in our study, we found minimal changes for a broad suite of soil and ground cover response variables relative to grazing but a strong influence of sampling timing (Badgery et al 2017, Van Syoc et al 2022. Importantly, stocking rate and vegetation structure outcomes in our two contrasting grazing treatments were similar as time was allowed to vary to achieve similar utilisation levels while animal density was different (Scasta et al 2023). Our findings of no response of soil organic carbon to grazing were similar to Henderson et al (2004), Li et al (2012), Shrestha and Stahl (2008), Derner et al (2018), and Briske et al (2008 but in contrast with those of Teague et al (2011).…”

“…Stocking rate and vegetation structure. Across treatments, the stocking rate averaged 2.22 (± 0.24) AUMs/ha in 2017, 3.03 (± 0.21) AUMs/ha in 2018, and 2.98 (± 0.31) AUMs/ha in 2019, and stocking 1), 50% forage allocation to cattle, and an animal unit (AU) equivalent to account for different animal types and sizes where the total predicted biomass available using herbaceous biomass calibration equations adjusted to a 50% standard allocation of forage to animals and then relativised for the number of animals of either heifers, cows + calves, or bulls based on an AU equivalent adjusted for animal size and calf age (here considered as 1.2 for heifers, 1.7 for cows, 2.2 for bulls), and 11.8 kg/day is the daily forage requirement relative to body weight (or in other words, 2.6% of animal body weight in air dry forage daily for a 454 kg cow with a calf which is the adjustment basis for an AU and then for 1 month to sustain 1 AU (i.e., an animal unit month or AUM) (Stam et al 2018, Scasta et al 2023 rate in 2017 was significantly lower than in 2018 and 2019 (P = 0.0041; Figure 3). Within the year, there were no stocking rate differences for treatments for any of the years (all P-values > 0.05; Figure 3).…”

“…The AUM concept is commonly applied when grazing rangelands in the western United States. Stocking details are explicitly presented in Scasta et al (2023) total MRG herd (heifers) weight was 5 380 animal kg/ha, and the approximate total UHD herd (cows with calves) weight was 67 812 animal kg/ha (Grazing Treatments described in Table 1). Grazing start date, end date, and animal numbers are described in detail in Table 2.…”

“…Comparison of annual mean stocking rates by grazed treatment for 2017-2019 at the University of Wyoming's James C. Hageman Sustainable Agricultural Research and Extension Center (SAREC) facility in Lingle, Wyoming, USA. Stocking rates were based on a parametrised grazing time model using herbaceous biomass (shown in Figure1), 50% forage allocation to cattle, and an animal unit (AU) equivalent to account for different animal types and sizes where the total predicted biomass available using herbaceous biomass calibration equations adjusted to a 50% standard allocation of forage to animals and then relativised for the number of animals of either heifers, cows + calves, or bulls based on an AU equivalent adjusted for animal size and calf age (here considered as 1.2 for heifers, 1.7 for cows, 2.2 for bulls), and 11.8 kg/day is the daily forage requirement relative to body weight (or in other words, 2.6% of animal body weight in air dry forage daily for a 454 kg cow with a calf which is the adjustment basis for an AU and then for 1 month to sustain 1 AU (i.e., an animal unit month or AUM)(Stam et al 2018, Scasta et al 2023…”