A novel life cycle assessment demonstrates that targeted genetic improvement can reduce the environmental impact of beef from beef × dairy production systems in the US and the UK.

Genetic improvement has been identified as a key practice for reducing the environmental impact of livestock systems through improved production efficiency. Beef-on-dairy (BxD) production comprises an increasingly large portion of beef supply chains and provides data collection opportunities for understanding the environmental impact of genetic improvement. Life cycle assessment (LCA) is the gold standard for measuring product-level environmental footprints and, to date, has not been applied to assess the mitigation potential of targeted genetic improvement in BxD production. The objectives of this study were to provide a framework for incorporating genetic improvement into an LCA, quantify the role of targeted genetic improvement in BxD production systems in the US and UK, and demonstrate the value of targeted genetic improvement as a key intervention for reducing the environmental impact of beef production. Life cycle assessments were completed for three BxD populations, a typical US feedlot system (US) and a premium (UK-HQ) and commodity (UK-HY) system in the UK. Each population was comprised of animals from two different genetic backgrounds: benchmark animals sired by industry average genetics, and genetically targeted animals (GT) sired by bulls from a breeding program targeting selection of traits that optimize BxD production. Within the benchmark and GT populations, animals were assigned to one of five genetic tiers, with five being the highest merit level, based on their sire's value for a BxD genetic index. Individual-level data were available for each of the growing phases, defined as weaning, rearing-milk, rearing-fed, grazing (UK-HQ only), and finishing. Average phenotypic performance in each sire tier was determined for average daily gain (ADG), days at the growing phase, feed dry matter intake (DMI) in finishing (US and UK-HY), and carcass weight. Using these performance averages, LCA runs evaluated each combination of genetic background (benchmark and GT), population (US, UK-HQ and UK-HY), sire genetic tier (Tier 1-Tier 5) and marketing year (2024 and 2029). The life cycle impact assessment characterized sixteen environmental impact categories covering water use and quality, land use, air quality, resource use, and climate change. Across all populations and sire genetic tiers, the main processes contributing to the relevant impact categories were feed production, manure management, and, for climate change only, enteric fermentation. The finishing phase had the largest impact among all growing phases, ranging from 50-89% of impact across the relevant impact categories. Higher genetic merit (i.e., higher sire tiers) consistently led to concurrent reductions across damage categories that aggregated to lower overall environmental impact. Comparisons of benchmark Tier 3 to GT Tier 5, representing the effect of genetic improvement, resulted in reductions in overall environmental footprint of -8.7% for the US, -9.6% for the UK-HY, and -4.2% for the UK-HQ populations in the 2024 marketing year, driven in part by climate change reductions of -4.7%, -8.8%, and -4.7%, respectively. This study demonstrates that genetic improvement in commercial systems for improved production efficiency confers systemic environmental benefits that accumulate over time, underscoring the value of targeted genetic improvement as a foundational practice for improving the sustainability of livestock production.