Snapshot of enteric methane emissions from stocker cattle grazing extensive semiarid rangelands

Authors: RAYNOR, EDWARD - Colorado State University; SCHILLING-HAZLETT, ASHLEY - Colorado State University; PLACE, SARA - Colorado State University; VARGAS, JUAN - Colorado State University; THOMPSON, LOGAN - Kansas State University; Johnston, Melissa; JORNS, TAMARAH - Natural Resources Conservation Service (NRCS, USDA); Beck, Matthew; Kuehn, Larry; Derner, Justin; STACKHOUSE-LAWSON, KIMBBERLY - Colorado State University

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2024
Publication Date: 1/26/2024
Citation: Raynor, E.J., Schilling-Hazlett, A., Place, S.E., Vargas, J.J., Thompson, L.R., Johnston, M.K., Jorns, T.R., Beck, M.R., Kuehn, L.A., Derner, J.D., Stackhouse-Lawson, K. 2024. Snapshot of enteric methane emissions from stocker cattle grazing extensive semiarid rangelands. Rangeland Ecology and Management. 93:77-80. https://doi.org/10.1016/j.rama.2024.01.001.
DOI: https://doi.org/10.1016/j.rama.2024.01.001

Interpretive Summary: A considerable knowledge gap for the beef cattle industry remains enteric methane (CH4) emissions from cattle grazing extensive semi-arid rangelands. Stocker (syn. yearling) operations need information on location-specific emissions values as cattle grazing forages represent a large portion of the enteric methane emissions from the US beef industry. This study evaluated enteric emissions on North American shortgrass steppe rangeland of locally-sourced steers and steers originating from mixed-grass prairie in south-central Nebraska. Our findings show local steers produced 20% more enteric CH4 emissions than non-locally sourced steers but also gained weight at three times the rate of non-local steers. This increased gain more than offset the higher animal emission production values of local steers, resulting in lower emission intensity (g CH4/ADG; EI) from local steers compared to the naïve steers (237.6 vs. 418.5 EI). Comparative efforts across rangeland ecosystems using animal origin as a key factor should lead to more accurate assessments grazing beef cattle sustainability related to greenhouse (GHG) gas mitigation strategies.

Technical Abstract: Enteric methane (CH4) emissions from cattle grazing extensive semi-arid rangelands are largely unknown and represent a considerable knowledge gap for the beef cattle industry. Knowledge of baseline enteric CH4 emissions is beneficial for understanding the range of variability in individual animal emission production (g CH4 head (hd)-1 day-1) and emission intensity (g CH4 kg-1 ADG-1). Here, we used field-based technology to determine enteric CH4 emissions from yearling steers grazing the North American shortgrass steppe in northeastern Colorado in mid-summer 2022. Twenty-six animals were acclimated for 30 days (1-30 June) to the sampling equipment in the field prior to the measurement of emissions (1-31 July). Twelve (46%) of these yearling steers fully acclimated, with mean CH4 emissions ranging from 113.3 to 261.7 g hd-1 day-1 across the sampling period. Daily CH4 production values were 20% higher for steers (n=9) from a local ranch compared with steers (n=3) that originated from a mixed-grass prairie in south-central Nebraska (202.63 vs. 169.03 g CH4 hd-1 day-1). Average daily gain (ADG) of local steers was three times greater than their counterparts (0.54 vs 0.18 kg hd-1 day-1), resulting in lower emission intensity (g CH4/ADG; EI) from local steers compared to the naïve steers (237.6 vs. 418.5 EI). In addition, we compared measured CH4 emissions with predicted emissions calculated using the IPCC tier 2 methodology; measured emissions were 31% greater than predicted for the local steers and 18% greater than steers from non-local steers. Results indicate that further research addressing grazing animal enteric CH4 emissions in extensive rangelands is needed. Further, efforts should be context-specific for comparative efforts across rangeland ecosystems and animal origin to inform more accurate assessments of sustainability of grazing beef cattle related to greenhouse (GHG) gas mitigation strategies.