Recommendations on visit duration and sample number requirements for an automated head chamber system

Authors: Beck, Matthew; THOMPSON, LOGAN - Kansas State University; REUTER, R - Oklahoma State University; Gunter, Stacey

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/21/2024
Publication Date: 6/4/2024
Citation: Beck, M.R., Thompson, L.R., Reuter, R.R., Gunter, S.A. 2024. Recommendations on visit duration and sample number requirements for an automated head chamber system. Journal of Animal Science. 102. Article skae 158. https://doi.org/10.1093/jas/skae158.
DOI: https://doi.org/10.1093/jas/skae158

Interpretive Summary: GreenFeed systems (C-Lock inc., Rapid City, SD) are being increasingly used for measuring carbon dioxide emissions (CO2), oxygen consumption (O2), and methane emissions (CH4) of free-roaming cattle. These systems utilize averages of multiple visits to provide estimates of daily gas flux. There currently exists a wide range of recommendations for what constitutes a “good” visit. Additionally, the number of recommended visits required to achieve adequate estimates of these gas flux appear to be dependent on the minimum visit duration that is used. To date, there has been only one experiment that has investigated visit duration and the recommended number of visits for CO2 and CH¬4 emissions and to our knowledge this has not been assessed for O2 consumption. Accordingly, scientists from ARS (Bushland, TX and Oklahoma), Kansas State University, and Oklahoma State University aimed to provide recommendations for visit duration minimum and number of required visits. It was determined that if a minimum visit duration of 2-minutes is used then 40 visits is needed and if 3-minutes is used then 30 visits are required.

Technical Abstract: Automated head chamber systems (AHCS; GreenFeed, C-Lock inc., Rapid City, SD) are being increasingly used for measuring gas flux of free-roaming cattle. There exists a wide range of recommendations for what constitutes a “good” visit (duration) to the AHCS and how many are required to the GreenFeed. Accordingly, the purpose of this experiment was to investigate the effects of visit duration thresholds and the subsequent effects of these thresholds on the number of visits needed to provide adequate estimates of carbon dioxide emissions (CO2), oxygen consumption (O2), and methane emissions (CH4) of beef cattle. This analysis utilized data from 4 previously published experiments. When comparing all available visits, there was excellent agreement [Lin’s concordance correlation coefficient (CCC) = 0.96] between visits =3 min. in duration and those =2 min. for the three gases for all four experiments. When all data were analyzed together, there was excellent agreement between visits =3 min. and those =2 min. and =1 min. for all gasses (CCC = 0.96). These results suggest that estimates from visits =2 min are similar to those from visits =3 min. Next, we investigated if including visits =2 min or =1 min would increase the minimal number of visits required to provide excellent agreement with the “gold-standard” (average of all visits =3 min). For this we utilized only one of the experiments and randomly selected visits ranging from n = 5-60, with increasing increments of 5. We then assessed the agreement between the “gold-standard” [average of all visits =3 min (n =144 ± 55.01)] estimates of CO2, O2, and CH4. The number of visits required to achieve excellent agreement (CCC = 0.90) to the “gold-standard” estimate for all gases was 30 or more for visits =3 min, was 40 or more for =2 min, and was not achieved for all gases when visits of =1 min were included. Based on these results, we recommend 30 minimum visits when =3 min durations are included and 40 minimum visits when =2 min durations are included.