Phenomics

Genetic Parameters for Methane Mass (g/day) and Methane Concentration (ppm) in Dairy Cattle

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Abstract

The objective of this study was to estimate and compare genetic parameters for enteric methane (CH4) emissions in Holstein dairy cows, in grams per day (g/day) provided by the GreenFeed system and converted back to the original concentration in parts per million (ppm) using the Ideal Gas Law. Several gas measurement technologies have been developed to quantify methane emissions in cattle. Among them, the GreenFeed system (C-Lock Inc., Rapid City, SD) is widely used and expresses methane output in g/day. However, methane concentration may be an alternate expression of methane emission for genetic evaluation. The Ideal Gas Law can be applied to non-linearly convert GreenFeed-derived methane mass back to concentration values to facilitate integration with databases expressed in concentration, such as from sniffers. Data were sourced from the Efficient/Resilient/NetZero Dairy Genome Projects collected from 2016 to 2025 at the Ontario Dairy Research Centre (Elora, ON, Canada) and comprised 12,574 GreenFeed records from 721 first-lactation Holstein cows. After excluding outliers using the interquartile range (IQR) method, 12,299 records remained. The pedigree comprised all known ancestors within 10 generations of the phenotyped animals. From all records, 5,159 g/day observations from 344 cows were successfully converted to ppm using the Ideal Gas Law, while 7,140 records (from 377 cows) lacked gas temperature information and were not converted. The Ideal Gas Law states that P*V = n*R*T, where n is the air molar flow rate, P is the atmospheric pressure (assumed 1 atm = 101,325 Pa), V is the Airflow converted from liters per second to cubic meters per second, R is the universal gas constant (8.314 J·mol⁻¹·K⁻¹), and T is the gas temperature in Kelvin (K). Using Ideal Gas Law, the air molar flow rate was estimated and methane production was converted from g/day to moles per second based on methane's molar mass (16.04 g/mol). The molar flow of methane was then divided by the molar flow of air to obtain the molar fraction, which was multiplied by one million to obtain the result in ppm. Weekly averages per animal were 493.0 ± 77.20 g/day and 234.2 ± 37.95 ppm. A bivariate mixed animal model was fitted, including the fixed effects of year-month combination and week within month and the random animal additive genetic effect. Heritability estimates were 0.37 ± 0.10 for g/day and 0.39 ± 0.11 for ppm. Genetic and phenotypic correlations were strong at 0.93 ± 0.05 and 0.90 ± 0.01, respectively. The overall correlation of estimated breeding values was 0.97. These findings indicate that methane emission expressed in g/day or ppm are strongly genetically and phenotypically correlated and similarly heritable, which may facilitate the integration of datasets expressed in CH4 mass (g/day) or concentration (ppm) and warrants further investigation.

Keywords: 2026

How to Cite:

Baes, C., Hermisdorff, I., Miglior, F., Schenkel, F. & Silva, E., (2026) “Genetic Parameters for Methane Mass (g/day) and Methane Concentration (ppm) in Dairy Cattle”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2286611. doi: https://doi.org/10.31274/wcgalp.24065

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