Increasing frequency and spatial extent of cattle heat stress conditions in the Southern plains of the USA.

Oklahoma, as part of the Southern Plains region and a key contributor to U.S. cattle production, faces increasing heat stress due to climate change, which can adversely influence livestock. We analyzed data from 121 Oklahoma Mesonet stations (1998-2022) to assess the spatio-temporal patterns of heat stress that influence cattle production across the state. Using the temperature humidity index (THI) and comprehensive climate index (CCI), we counted the number of days that exceeded critical thresholds for cattle production. Based on THI, only 12% of stations showed a significant increase in heat stress, while more than 60% did based on CCI, driven mainly by significantly lower summer wind speeds. Statewide cattle and calf inventory data showed a significant decrease in cattle numbers, especially following years with a large number of heat stress days based on CCI. At the county level, decreasing inventory often aligned with increasing heat stress, which suggested a strong relationship between heat stress and cattle health. With the number of heat stress days increasing by up to four days per year, adaptive strategies are crucial to mitigate the negative impacts of heat stress on cattle health and productivity in this region.