Associations of Behavioural Activity and Environmental Conditions with Milk Production and Composition in Dairy Cows.

The present study investigated the relationships between behavioural traits, environmental conditions, and milk production and composition in dairy cows using data obtained from an automated behavioural monitoring system. A total of 283 observations collected from 19 Holstein Friesian and Simmental cows were evaluated. Behavioural traits, including activity, eating, and rumination time, were recorded using the CowManager SensOor system, while environmental conditions were assessed using the temperature-humidity index (THI). Morning milk yield and milk composition traits were evaluated in relation to behavioural, environmental, and lactation-related factors using linear mixed-effects models. Milk yield decreased with advancing lactation stage, whereas milk protein and lactose concentrations increased. Increasing THI was negatively associated with morning milk yield in the initial analysis, but this association did not remain significant after adjustment for multiple comparisons. In contrast, THI was positively associated with milk pH, although the magnitude of this association was small. Behavioural variables showed limited associations with milk production and major milk composition traits; however, eating time was negatively associated with milk electrical conductivity after adjustment for multiple comparisons. Overall, the findings indicate that environmental conditions and lactation stage are important sources of variation in milk production and composition, whereas automated behavioural measurements may provide complementary information on selected milk quality characteristics. These results highlight the potential of sensor-based behavioural monitoring as a complementary tool for evaluating dairy cow performance under variable environmental conditions.