Impact of Blood Metabolic Profile and Ingestive Behaviours Registered with Noseband Sensor on Methane Emission During Transition Period in Dairy Cows

This study investigates the relationship between methane emissions and physiological, behavioural, and haematological parameters in dairy cows during the transition period. Methane emissions were monitored alongside variations in rumination, feeding behaviour, and blood markers three weeks before calving, on calving day, and three weeks post-calving. Cows were retrospectively classified into low, medium, and high rumination groups according to their average daily rumination duration to investigate the effects of behavioural influences. During the prepartum period, the methane concentration was moderately positively correlated with drinking time (r = 0.41, <i>p</i> < 0.01) and weakly negatively correlated with chews per minute (r = -0.358, <i>p</i> < 0.05). Significant negative correlations were noted with chloride (r = -0.42, <i>p</i> < 0.01) and glucose levels (r = -0.41, <i>p</i> < 0.01). Following calving, methane emissions showed a positive correlation with haematocrit (r = 0.41, <i>p</i> < 0.01) and a negative correlation with haemoglobin (r = -0.47, <i>p</i> < 0.01). A haematological analysis revealed a notable negative correlation with platelets during calving (r = -0.64, <i>p</i> < 0.05). Individual dry matter intake (DMI) was recorded for each period, showing a significant drop on calving day. This intake fluctuation coincided with a significant rise in methane yield on calving day (<i>p</i> < 0.001). In the low rumination time group, methane was moderately negatively correlated with rumination chews (r = -0.52, <i>p</i> < 0.05), while in the high rumination group, a moderate negative correlation was observed with drinking gulps (r = -0.42, <i>p</i> < 0.05), and a weak negative correlation was observed with bolus events (r = -0.37, <i>p</i> < 0.05). Despite behavioural variations, methane emissions showed no substantial differences among groups with low, medium, and high rumination times, suggesting a minimal direct influence on rumination duration. These findings emphasise the complex interactions between feed intake, metabolism, and methane emissions, underscoring the importance of integrating behavioural and physiological indicators to develop targeted strategies for enteric methane mitigation while providing baseline data from healthy cows that could guide future research on methane emissions in cows undergoing postpartum metabolic disorders.