Sustainability & efficiency

Genetic variation for methane emissions and meat fatty acid composition in a New Zealand sheep population implicates rumen microbiome metabolism

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Abstract

The New Zealand economy has 5.1% of GDP and 70% of exports from agricultural products and has made international commitments to reduce atmospheric emissions in the 2016 Paris Agreement. Methane (CH4) is a relatively potent greenhouse gas with a shorter half-life than carbon-dioxide (CO2) which is primarily emitted from ruminant livestock. Rumination produces fatty acids in a variety of host and microbial metabolic pathways. Breeding using genomic selection is viable to reduce emissions of CH4 from ruminant livestock while preserving genetic gains for productivity traits. Accurately phenotyping CH4 emissions in livestock is costly, laborious, and difficult to scale or deploy on-farm in remote areas. The impacts on meat quality also remain relatively unexplored. This study is part of a joint New Zealand and Ireland project (Methane-Predict) to investigate these relationships.It is hypothesized that heritable changes in the rumen microbiome and fatty acid metabolism are related to lower CH4 emissions. Measurements for CH4 emissions using portable accumulation chambers (PAC) and composition of 63 fatty acids in loin meat samples have been collected from 686 individual 6 months-old lambs at an individual level. This dataset from 3 New Zealand flocks with composite breeds is the largest to date and includes rare fatty acids that are often overlooked in gas chromatography reports. A bivariate analysis was performed using ASReml v4.2 with industry-standard fixed effects for scaled PAC daily CH4 emissions and each fatty acid.Heritability estimates of PAC were consistent with previous studies with a range [0.206, 0.282]. For meat fatty acids, heritabilities varied betweeen [0.01, 0.758] and phenotypic correlations varied between [-0.211, 0.122]. Saturated odd-length fatty acids (C15:0 and C17:0) and their methylated branch chain variants were inversely correlated with scaled daily CH4 estimates. In contrast, poly-unsaturated fatty acids were positively correlated with high daily CH4 estimates. C15:0 and C17:0 being over-represented in low CH4 samples indicates that rumen microbiome metabolism plays a key role as these fatty acids cannot be produced by human or animal metabolic pathways.These results demonstrate that meat fatty acids may be a viable proxy trait to estimate CH4 emissions in livestock ruminants. Further work is needed to evaluate whether these results are robust in a larger sample size with a wider genetic background, diverse climates or feeding conditions, and whether the insights can be applied in other countries. To achieve this a similarly large dataset is being collected in Ireland. It is possible that differences in fatty acid composition could improve product quality in addition to being utilised for cost-effective screening of low emissions traits. Further investigation of the rumen microbiome composition could shed light on the underlying relationship between host genetics, meat fatty acid composition, and CH4 emissions at an individual animal level.

Keywords: 2026

How to Cite:

Agnew, M., Bain, W., Bilton, T., Booker, F., Dodds, K., Hampton, I., Johnson, P., Kelly, S., McEwan, J., McRae, K., Peers-Adams, J., Rowe, S. & Shortall, A., (2026) “Genetic variation for methane emissions and meat fatty acid composition in a New Zealand sheep population implicates rumen microbiome metabolism”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2283758. doi: https://doi.org/10.31274/wcgalp.23511

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