Comparing energy intake estimates derived from using respiratory gas flux measurements with backward dietary energy partitioning for beef cattle

Authors: Gunter, Stacey; Moffet, Corey; BELL, COLLEEN - Former ARS Employee; GREGORINI, PABLO - Lincoln University - New Zealand

Submitted to: Journal of Agriculture and Food Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2025
Publication Date: 4/16/2025
Citation: Gunter, S. A., Moffet, C. A., Bell, C., Gregorini, P. 2025. Comparing energy intake estimates derived from using respiratory gas flux measurements with backward dietary energy partitioning for beef cattle. Journal of Agriculture and Food Research. 21. Article 101912. https://doi.org/10.1016/j.jafr.2025.101912.
DOI: https://doi.org/10.1016/j.jafr.2025.101912

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 forages 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: Objective: The objective of this experiment was to refine the use of open-circuit gas-quantification methodology when estimating energy intake and to compare 4 different methods to account for urinary N excretion (UN). Materials and Methods: Eight cross-bred beef steers (BW = 244 ± 15.1 kg) were used in a 77-d feeding experiment. Steers were housed in a pen equipped with individual feeders and access to an automated head chamber system (AHCS; GreenFeed, C-Lock Inc., Rapid City, SD). Steers were then randomly assigned to 1 of 3 multiples of maintenance energy intake (10.7 Mcal of ME/kg daily): 1.1 × (1.1M, n = 3), 1.4 × (1.4M, n = 2), and 1.8 × (1.8M, n = 3). Diets were fed as long-stemmed wheat (Triticum aestivum L.) hay and alfalfa pellets via the AHCS. Heat production (HP) was estimated using the Brouwer (1965) equation and UN was accounted for with 1 of 4 approaches; these included prediction models based on DMI and diet quality or BW; assuming a constant value of 60 g/d; or assume UN was 0. Results and Discussion: Respiration gas fluxes and BW gain increased with increased feeding rates from 1.1M to 1.8M. Hence, HP and energy retention translated to an increased ME, DE, and GE intakes. Pearson correlations and Lin’s concordance of correlation coefficient (rc) between estimated GE, DE, and ME intake and measured values were highly positive (r = 0.91; rc = 0.47) regardless of method used for UN excretion. Implications and Applications: Energy intake estimated from gas flux and BW gain seems to be a useful metric for the evaluation of the energetics of grazing or group-fed cattle. Last, multiple short-term breath measurements from an AHCS, together with BW change, can be used to estimate the energy intake by cattle.