Mapping risk of heat stress for dairy cattle in Tigray Regional State, Northern Ethiopia

This study aimed to assess the risk of heat stress conditions for dairy cattle in the Tigray regional state of Ethiopia under historical and future climatic conditions. The daily thermal heat index (THI) was computed for each of the 14 weather stations after quality control of the maximum and minimum temperature datasets. The calculations were performed for the historical period (1980–2023) and two future climate periods (mid-term: 2040–2069 and end-term: 2070–2099) using an ensemble of 20 global circulation models under two representative concentration pathways (RCP 4.5 and 8.5). During the historical period, the frequency of severe heat stress was 3.4% (13 days/year), predominantly occurring in the western corner of the region (39.5% of days/year). The frequency of projected severe heat stress days across the region is expected to increase to 5.4% (mid-term) and 6% (end-term) under the RCP 4.5 emission scenario. Under the RCP 8.5 scenario, the frequency is expected to rise to 6.2% (mid-term) and 9.4% (end-term). On average, there were 6–9 consecutive severe heat stress days in both the historical and future climate periods. It is crucial to emphasize that the mapping of heat stress risk in dairy cattle was carried out using THI thresholds developed elsewhere. However, it is imperative to underscore the significance of conducting local experiments to determine context-specific thresholds.