We determined climate change-driven heat stress risk for outdoor dairy cows in New Zealand’s pasture-based systems. Using climate projections from 2006 to 2098, we calculated temperature–humidity index and grazing heat-load index values, which indicated that THI may not fully capture outdoor heat stress dynamics, with solar radiation and wind speed playing critical roles. Key dairy regions in New Zealand already experience high heat stress risk and are projected to experience intensified risk in the future, necessitating adaptation strategies such as shade provision, genetic selection, and modified feeding practices.

This article belongs to the collection: Australasian Dairy Science Symposium 2024.