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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Agroecosystems Management Research » Research » Publications at this Location » Publication #433217
Research Project: Physiological, Microbiological, and Nutritional Mechanisms to Maintain Animal Productivity in the Absence of Antibiotics

Location: Agroecosystems Management Research

Title: Carbon mass balance in growing-finishing pigs

Author
item Kerr, Brian
item Trabue, Steven
item HUMPHREY, DALTON - Iowa State University
item SHURSON, GERALD - University Of Minnesota

Submitted to: Frontiers in Animal Science
Publication Type: Review Article
Publication Acceptance Date: 6/30/2026
Publication Date: 8/5/2026
Citation: Kerr, B.J., Trabue, S.L., Humphrey, D.C., Shurson, G.C. 2026. Carbon mass balance in growing-finishing pigs. Frontiers in Animal Science. https://doi.org/10.3389/fanim.2026.1845357.
DOI: https://doi.org/10.3389/fanim.2026.1845357

Interpretive Summary:

Technical Abstract: Carbon (C) is widely distributed in nature and forms more compounds than all other elements combined. However, when more C is released into the atmosphere as carbon dioxide (CO2) and methane (CH4) than can be reabsorbed by plants, the global ecosystem then becomes imbalanced. Although pigs emit less CO2 and CH4 than ruminants, accurate accounting of the C mass balance and emissions in swine production systems is needed for developing feeding strategies to improve C use efficiency (CUE) and to accurately estimate the carbon footprint of pork supply chains. Improvement in CUE minimizes C losses into the environment, optimizes natural resource use, enhances food security, and improves the economic and environmental sustainability of pork production. Thermal combustion analysis is the most common method for determining total C concentrations in a wide variety of matrices. Analytical results of the C concentration in 80 feed ingredients were highly variable (0.02 to 77% C) within and among feedstuff classifications. There was a strong positive association between fecal C and gross energy (GE) excretion (r = 0.998; P < 0.001) and between urinary C and GE excretion (r = 0.934; P < 0.001), with C excretion corresponding to a daily loss of 10.55 kcal GE/g of C excreted in feces and a loss of 11.91 kcal GE/g of C excreted in urine. On a mass-balance basis, about 14% of dietary C intake is excreted in feces, 2% is excreted in urine, and 25% retained in the whole body as protein and fat. Depending on the method and assumptions used, exhaled C (i.e., CO2 and CH4) represents the greatest loss of C, representing 50% to 55% of dietary C intake. These results indicate that dietary CUE in growing-finishing pigs is relatively poor (about 25% of C intake) and may be further reduced in pigs subjected to heat stress, immune challenges, and other metabolic disruptions that occur under commercial production conditions.