Associations between space-use behaviour and temperature-humidity index in barn-housed dairy cows

Cattle may modify their space-use behaviour as thermal conditions change within their environment. Here we examined the relationship between the temperature-humidity index (THI) and various space-use metrics in a UK barn-housed dairy cow herd. Using a real-time local positioning system, as part of a precision livestock farming (PLF) approach, we continuously tracked the spatial position and activity of cows at high temporal resolution from 1st June to 1st December 2024. Localised ambient barn temperature and relative humidity were also continuously monitored within the barn. We assessed the amount of time individuals spent in key resource areas, their activity levels, distance travelled, and z-axis values, as well as bunching behaviour based on four metrics: range size (individual and herd), intercow distance (ICD) and nearest neighbour distance (NND). Cows spent more time near water troughs and fans as THI increased, and less time in the feeding zone under higher THI, except during early morning hours. Time spent in the cubicle area varied by time of day. Activity increased with rising THI except during the late evening. When high sensor-recorded activity values were recorded, cows travelled further with increasing THI during the day. Additionally, z values increased with increasing THI during the day, suggesting cows spent more time standing. Bunching behaviour also changed with increasing THI: ICD decreased and individual range size increased. Patterns for NND were unclear. Monitoring space-use metrics such as proximity to resources and bunching behaviour, alongside activity levels, may provide early behavioural indicators of heat stress in livestock. Further research is needed to assess the generality of these indicators across different barn environments, to help inform welfare and production management.