Using respiratory gas flux and backward dietary energy partitioning to estimate energy intake by beef cattle when fed a high-concentrate diet

Authors: Friend, Emalee; Gunter, Stacey; Womack, Addie; BECK, PAUL - Oklahoma State University

Submitted to: Animal - Open Space
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/7/2025
Publication Date: 11/13/2025
Citation: Friend, E., Gunter, S.A., Stamps, A.M., Beck, P. 2025. Using respiratory gas flux and backward dietary energy partitioning to estimate energy intake by beef cattle when fed a high-concentrate diet. Animal - Open Space. 4. Article 100113. https://doi.org/doi:10.1016/j.anopes.2025.100113.
DOI: https://doi.org/10.1016/j.anopes.2025.100113

Interpretive Summary: Improving cattle production traits, such as growth rate, fertility, and efficiency of feed conversion by breeding and precision management will reduce net greenhouse gas emissions because fewer animals will be needed to produce the same amount of product. Accordingly, improved animal energetic efficiency is advocated to reduce net greenhouse gas emissions from ruminant production systems. Automated head chamber systems that measure the respiration gas fluxes by grazing cattle have become more popular as animal and environmental scientists and managers gain a greater understanding of their function and potential research and production uses. The initial head automatic chamber systems were primary designed to measure enteric methane and carbon dioxide emissions. As the technology advanced and users had a better understanding of the appropriate operation and management of these head chamber systems and confidence was gained in the quality of emission estimates, other sensors to measure various respiratory gases have become available. ARS researchers reported the first data from an automatic head chamber that oxygen consumption estimates were available because of the installation of a parametric oxygen sensor. This experiment confirmed that energy intake by cattle consuming concentrate diets can be estimated using multiple short-term breath measurements from these head chamber systems, together with measured body weight and shrunk average daily gain. This approach has high precision and good to excellent accuracy when measurements are made over an extended period.

Technical Abstract: Twelve Charolais steers (initial shrunk BW = 223 ± 21.5 kg) were used in a 73-day feeding experiment to evaluate the use of methane (CH4) and carbon dioxide (CO2) emissions, and oxygen (O2) consumption as biomarkers in estimation of energy intake in growing beef cattle when integrated with backward dietary energy partitioning calculations when fed a high-concentrate diet. Steers were housed in a pen equipped with Calan gates (American Calan Inc., Northword, NH) with access to an automated head chamber system (AHCS; GreenFeed, C-Lock, Inc., Rapid City, SD). Steers were randomly assigned to 1 of 3 treatments according to dry matter (DM) intake as multiple of maintenance, which are 1.1 (1.1M, n = 4), 1.4 (1.4M, n = 4), and 1.8 (1.8M, n = 4) of a 29.3 megajoule (MJ)/kg diet. The diet fed was 350 g of chopped sorghum hay (crude protein = 64 g/kg of DM; in vitro digestibility = 578 g /kg of organic matter (OM)) and 650 g of concentrate (CP = 191 g/kg of DM; in vitro digestibility = 918 g/kg of OM). The concentrate consisted of 418 g of flaked corn, 85 g of cottonseed meal, 130 g of distillers’ grain, and 175 g of limestone/kg of DM. Steers were supplemented daily with 1.0 kg of alfalfa pellets (Medicago sativa; CP = 166 g/kg of DM; in vitro digestibility = 870 g/kg of OM) that were fed through the AHCS as bait. Methane tended (P = 0.07), and CO2 emissions and O2 consumption (P < 0.01) increased with the increasing feeding rates. Calculated gross energy (GE; 71.4, 86.9, and 106.7 MJ/d, respectively), digestible energy (DE; 61.1, 72.1, 86.7 MJ/d, respectively), and metabolizable energy (ME; 50.35, 60.19, 73.30 MJ/d, respectively) intake increased concurrently with the increases in energy retention and heat production. The predicted values for GE (63.1, 78.3, and 93.9 MJ/d, respectively), DE (52.8, 63.9, and 73.6 MJ/d, respectively), and ME (42.0, 52.0, and 60.2 MJ/d, respectively) intake rates increased concurrently with the increase from 1.1M to 1.8M. Pearson correlation of calculated and predicted GE, DE, and ME intake rates agreed closely (r = 0.95, 0.88, 0.85, respectively). This experiment shows that with multiple short-term breath measurements from an AHCS, BW, and an estimate of average daily gain that GE, DE, and ME intakes by cattle consuming a high-concentrate diet can be predicted.