Dormant season grazing on northern mixed grass prairie agroecosystems: Does protein supplement intake, cow age, weight and body condition impact beef cattle resource use and residual vegetation cover?

PLoS One. 2020 Oct 13;15(10):e0240629. doi: 10.1371/journal.pone.0240629. eCollection 2020.

Abstract

Dormant season livestock grazing reduces reliance on harvested feeds, but typically requires protein supplementation to maintain animal performance. Individual variation in supplement intake can impact animal performance; however, it is unknown if this variation leads to individual or herd-level effects on grazing behavior, resource utilization, and grazing impacts to native rangelands. To examine effects of protein supplementation on dormant season cattle resource use and, subsequently, post-grazing habitat conditions, we examined cattle grazing behavior, resource utilization and biomass removal of vegetation on a native rangeland in Montana. A commercial herd of 272 (yr 1) and 302 (yr 2) cows grazed a 329-ha rangeland pasture from November to January. Intake of a 30% crude protein supplement was measured for each individual. Five individuals within each of six age groups were equipped with GPS collars. Time spent grazing declined with supplement intake ([Formula: see text] = -0.05 ± 0.02; P < 0.01). Distance traveled per day had a positive asymptotic association with supplement intake ([Formula: see text] = 0.35 ± 0.09; P < 0.01). On average, resource utilization by cattle grazing dormant season forage decreased with terrain ruggedness ([Formula: see text] = -0.09 ± 0.03), but was unrelated to aspect, temperature and wind speed. Notably, we observed high individual variability in resource utilization for elevation, distance from supplement and water. A post-hoc analysis suggested that individual attributes (age, body weight, supplement intake) influenced cattle resource use. At moderate stocking rates, dormant season livestock grazing did not affect residual vegetation conditions (P values > 0.22). However, residual cover of forbs and litter increased with relative grazing intensity ([Formula: see text] = 1.04 ± 0.41; [Formula: see text] = 3.06 ± 0.89; P ≤ 0.05). In summary, high individual variability in grazing resource utilization of cattle suggests individual-level factors could be the dominant drivers in grazing behavior and landscape use.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Age Factors
  • Animal Distribution / physiology
  • Animal Feed*
  • Animal Husbandry / methods*
  • Animal Nutritional Physiological Phenomena
  • Animals
  • Biological Variation, Population
  • Body Weight / physiology
  • Cattle
  • Dietary Proteins / administration & dosage*
  • Dietary Supplements*
  • Grassland
  • Herbivory / physiology*
  • Montana
  • Seasons

Substances

  • Dietary Proteins

Grants and funding

National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 2015-38640-23779 through the Western Sustainable Agriculture Research and Education program under sub-award number (GW17-040). https://www.westernsare.org/ • SW, JGPB, LM The Bair Ranch Foundation • SW, JGPB, DB The Nancy Cameron Endowment • TD, SW The Montana Stockgrowers Association. https://mtbeef.org/ • TD, SW The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.