Sustainability & efficiency

Methane Trait Inclusion in Beef Terminal Indices under Increasing Carbon Pricing

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Abstract

There is a lack of consensus on the optimum method for including enteric methane in beef breeding objectives. Ireland's beef terminal index already includes a carbon sub-index based on a complete life cycle analysis (LCA) where the carbon costs of various traits are included. The present study compared different versions of Ireland's terminal index with or without the explicit inclusion of an enteric methane trait assuming a carbon price of €80, €160, or €320/t CO₂e.Enteric methane was measured on 1,700 beef cattle using GreenFeed systems between 2018 and 2025. Two enteric methane EBVs were calculated using multi-trait animal models that included energy intake and carcass weight: gross methane EBVs (genetic SD = 23.43 g/d) and residual methane EBVs (genetic SD = 20.34 g/d) representing enteric methane genetically independent of energy intake and carcass weight. Three index scenarios were evaluated at each carbon price using AbacusBio's Selection Index Testing tool: (1) LCA-based carbon weighting only on relevant traits (status quo); (2) LCA-based weighting without enteric methane but with gross methane EBV included explicitly; (3) current LCA-based weighting plus residual methane EBV. Index performance was dictated by expected response to selection (over 10 years) and AI sire rankings separately across 180 Angus, 130 Charolais, 192 Limousin, and 1,138 multibreed populations.At €80/t CO₂e, the within and across-breed correlations among all three explored terminal index constructs were not different from 1 (P >0.05), indicating minimal sire re-ranking. The LCA-based carbon weighting produced breed-specific enteric methane responses: +0.32 g CH₄/d for Charolais but reductions of -0.50 (Limousin) to -1.39 g CH₄/d (multibreed) over 10 years. Including measured enteric methane EBVs provided minimal additional methane response (At €160/t, the LCA-based carbon weighting produced enteric methane responses from -0.63 to -1.54 g CH₄/d (Angus, Limousin, multibreed) to +0.26 g CH₄/d (Charolais) while expected genetic gain in carcass weight remained at 90% of baseline. Including gross methane EBVs achieved additional enteric methane reductions of -0.04 to -0.20 g CH₄/d while increasing carcass weight gains up to 0.07 kg. At €320/t, the LCA-based carbon weighting achieved enteric methane responses from -1.73 g CH₄/d (multibreed) to +0.21 g CH₄/d (Charolais), with expected genetic gain in carcass weight at 77-96% of baseline. Adding gross methane EBVs delivered additional reductions of 0.03 to 1.23 g CH₄/d with carcass weight gains at 93-100% of baseline, while residual methane EBVs achieved reductions of 0.00 to 0.86 g CH₄/d with carcass weight gains at 97-107% of baseline.Although minimal sire re-ranking occurred, having access to enteric methane EBVs enables farmers to differentiate among bulls of comparable economic merit and select those with superior genetic merit for reduced methane emissions.

Keywords: 2026

How to Cite:

Amer, P., Berry, D., Conroy, S., Crowley, S., Hely, F. & Kelly, D., (2026) “Methane Trait Inclusion in Beef Terminal Indices under Increasing Carbon Pricing”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2285123. doi: https://doi.org/10.31274/wcgalp.23634

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