Integrating climate scenarios and thermal welfare thresholds to project future heat stress risk in beef cattle.

Global demand for beef is projected to rise, coinciding with increasing climate change-related threats to animal welfare and productivity. Heat stress represents a major risk, impairing cattle health, growth, and reproductive efficiency. This study employed the Heat-Load Index, a composite measure of temperature, humidity, solar radiation, and wind speed, to classify heat stress into five categories. Using high-resolution climate projections from the NEX-GDDP-CMIP6 archive and a Multi-Model Ensemble of 27 global circulation models, we assessed heat stress risk for beef cattle worldwide under four Shared Socioeconomic Pathways (SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5) through 2100. Results indicated a progressive expansion of severe and extreme heat stress categories, particularly in tropical and subtropical regions, with increasing encroachment into temperate zones by the late century. These findings highlight the urgent need for climate-smart livestock strategies, including genetic selection, improved housing, and adaptive management, to safeguard animal welfare and sustain global beef production.