BeefAI™ — Genetic Emissions Intensity Score (GEIS): Methodology for Scoring Bull Genetic GHG Reduction Potential from BREEDPLAN® EBVs in Australian Angus Cattle

Background: Enteric methane from grazing beef cattle is a large and structurally difficult-to-abate component of Australian agricultural GHG emissions. Nutritional interventions are largely confined to feedlot settings; genetic improvement is the only tool capable of producing permanent, cumulative, and system-wide reductions across the 95% of emissions arising from pasture-based herds. The peer-reviewed literature confirms that methane yield (MY) and net feed intake (NFI) are moderately heritable traits (~0.26–0.43) with substantial natural variation between individual animals and between sires, making them tractable selection targets. Purpose: This paper documents the methodology for the BeefAI™ Genetic Emissions Intensity Score (GEIS) a composite bull-level score quantifying the expected genetic contribution to reducing GHG emissions intensity (kg CO₂-e per kg liveweight produced) in the progeny herd, derived from BREEDPLAN® EBVs available in the TransTasman Angus Cattle Evaluation (TACE). GEIS combines three existing BeefAI™ scoring layers the Methane Emission Intensity (MEI) Proxy (40%), the Net Feed Intake (NFI) direct score (35%), and the Carbon Efficiency of Reproduction (CER) (25%) using empirically justified weights derived from the published livestock GHG genetics literature. All components are proxy-based, deriving from routinely available TACE EBVs; no direct methane measurement EBV is currently available in BREEDPLAN® at commercial scale, and GEIS is explicitly framed as an indirect genetic proxy, not a certified emissions reduction claim. Conclusion: The scientific literature supports expected herd-level enteric methane reductions of 0.75–1.0% per year through selection for feed efficiency (Basarab et al. 2013), with low-RFI cattle demonstrating 15–25% less enteric CH₄ than high-RFI contemporaries at equivalent production levels. Combining low methane yield selection with low-RFI selection may reduce methane emissions by 40–45% over a breeding horizon (Pickering et al. 2013). GEIS quantifies a bull's genetic contribution to this trajectory on a 0–100 scale, sitting as the genetic layer of BeefAI™'s three-layer Carbon Passport™ framework alongside paddock-level NEE sequestration evidence (Doc A) and paddock GHG balance scenario modelling (Doc B).