Enteric methane emissions in grazing dairy systems

Authors: Soder, Kathy; BRITO, ANDRE - University Of New Hampshire

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2023
Publication Date: 6/29/2023
Citation: Soder, K.J., Brito, A.F. 2023. Enteric methane emissions in grazing dairy systems. Journal of Dairy Science. 4(4):324-328. https://doi.org/10.3168/jdsc.2022-0297.
DOI: https://doi.org/10.3168/jdsc.2022-0297

Interpretive Summary: Grazing dairy and livestock systems have been targeted as a source of enteric greenhouse gas emissions, primarily due to decreased forage quality that frequently results in increased enteric methane emissions. Compared with confinement operations where feeding rations and conditions are more controlled, grazing systems provide additional challenges due to lack of control of diet quality and difficulty in quantifying dry matter intake and methane emissions of cows on pasture. There are also fewer options for mitigating methane emissions in grazing cows than in confined cows due to less control of the diet as well as potential milk markets such as grassfed or organic that restrict supplementation strategies. This invited review covered current and potential animal and forage management strategies to mitigate enteric methane emissions that would be applicable to grazing dairy systems. Additionally, many assessments of the impact of grazing livestock systems do not account for the ecosystem services provided by grazing systems which could offset much, if not all, of the enteric methane produced by grazing dairy cows. Life cycle assessments that account for the carbon flux of all inputs and outputs of grazing dairy systems are needed to fully assess overall environmental impact.

Technical Abstract: Grazing systems have been targeted as a particular source of enteric greenhouse gas emissions, primarily due to decreased forage quality and digestibility and reduced feed efficiency that frequently result in increased enteric CH4 emissions. Compared with confinement operations, grazing systems provide additional challenges due to lack of control of diet quality and difficulty in quantifying dry matter intake and CH4 emissions of cows on pasture. While emerging technologies are making gaseous data collection feasible and less laborious in extensive environments, robust data sets on enteric CH4 emissions under grazing conditions are still lacking. Likewise, effective and economically feasible strategies to mitigate enteric CH4 emissions in grazing dairy cows are limited. This review will cover current and potential animal and forage management strategies to mitigate enteric CH4 emissions that would be applicable to grazing dairy systems. Additionally, many assessments of the impact of grazing livestock systems do not account for the ecosystem services provided by grazing systems which could offset much, if not all, of the enteric CH4 produced by grazing dairy cows. Life cycle assessments that account for the C flux of all inputs and outputs of grazing dairy systems are needed to fully assess overall environmental impact.