Gas flux determination and prediction of methane emissions in yearling steers under grazing conditions

Authors: VARGAS, J - Colorado State University; PAULA, E - Colorado State University; Derner, Justin; ENNS, R - Colorado State University; SCHILLING-HAZLETT, A - Colorado State University; KUTZ, M - Colorado State University; Kuehn, Larry; Johnston, Melissa; RITTEN, JOHN - Colorado State University; DELAY, NATHAN - Colorado State University; THOMPSON, L - Kansas State University; CAMPOS, L - Colorado State University; SHADBOLT, ANNA - Colorado State University; RAYNOR, EDWARD - Colorado State University; CARVALHO, PEDRO - Colorado State University; STACKHOUSE-LAWSON, KIM - Colorado State University; PLACE, SARA - Colorado State University; MESA, I - Colorado State University

Submitted to: Animal Production Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/3/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary: New technology for evaluating individual animal gas flux measurements could be used to assist ranchers/livestock producers in identifying high efficiency animals for operations. One novel technology is the automated head chamber system (AHCS) which has been used in many experiments with confined cattle, but similar efforts for cattle in extensive grazing systems are lacking. Knowledge of what is the minimum number of AHCS visits needed for reliably determining an individual’s gas flux measurements in pastures and rangelands would be helpful for researchers working with ranchers and livestock producers. We measured individual gas flux from a total of 141 yearling cross-bred yearling steers grazing on improved pastures or native shortgrass steppe rangeland. We determined that at least 55 visits to the ACHS by a steer was needed to adequately represent gas flux emissions under grazing conditions. This information is helpful for ongoing and new studies on extensive rangelands and pasture systems such that researchers can provide robust information and findings to ranchers and livestock producers regarding the efficiency of their individual animals.

Technical Abstract: TThe use of an automated head chamber system (AHCS) for determining methane emissions in ruminants has increased in recent years; however, assessments of emissions from cattle in grazing systems remain limited, constrained by a lack of knowledge regarding the minimum number of AHC visits needed for gas flux measurements. Additionally, appropriate methane determination allows the evaluation of existing models for predicting methane emissions from cattle under grazing conditions. This study aimed to determine the minimum number of AHCS visits to determine gas flux and to evaluate the sensitivity of retrieved equations for estimating enteric methane emissions in yearling steers under grazing conditions. Individual gas flux from a total of 141 yearling cross-bred steers (398 ± 53.0 kg of body weight [BW]) that visited the AHCS at least 100 times under grazing was included in the analysis. Gas flux variables for each steer were estimated by increasing 5-visit intervals until the full 100-visit dataset was utilized. Residual variance, Pearson correlation, and Spearman rank correlation were calculated to determine the minimum number of AHCS visits to determine gas flux compared to the total 100-visit dataset. Then, 31 retrieved equations to estimate methane production were evaluated according to the individual methane emission from 154 yearling steers (394 ± 54.1 kg BW), using root mean square prediction error (RMSPE) and concordance correlation coefficient (CCC) analysis. Steers required at least 55 visits to ACHS to represent gas flux emissions under grazing conditions compared to the mean gas flux of 100 visits, resulting in Spearman and Pearson coefficient correlations greater than 0.95. In addition, four equations for predicting methane emissions had excellent agreement (i.e., RMSPE ranged between 15.6 and 19.0 g/d and CCC ranged between 0.83 and 0.86) with individual methane production, using the 55-visit average of methane production. In the evaluated grazing environments, yearling steers required at least 55 visits to represent the gas flux, using the ACHS. In this analysis, four equations had excellent agreement between predicted and observed CH4 emissions in the evaluated yearling steers under grazing conditions.