Linking Methane Emissions with Health Indicators in Dairy Cows Across the Peripartum Period

Objectives: The dairy industry confronts difficulties in improving productivity while reducing environmental impacts, particularly enteric methane emissions, a major greenhouse gas that could intensify global warming. We must recognise the calving period due to its potential influence on methane emissions due to physiological alterations. This study utilises innovative technologies to monitor bovine behaviour and associate methane emissions with physiological metrics to improve our comprehension of their relationship. Blood metabolites indicate metabolic health, suggesting that metabolic status may affect methane emissions. This approach clarifies the biological factors influencing methane production by combining behavioural and physiological data, thereby enabling focused emission reduction strategies in the dairy industry. Materials and Methods: The research, carried out in Lithuania from November 2023 to April 2024, observed 13 healthy dry Holstein cows beginning 40 days prior to calving and lasted for 7 weeks. RumiWatch sensors (RumiWatch System, Itin+Hoch GmbH, Liestal, Switzerland) were utilised to monitor feeding and activity behaviours, while methane emissions were assessed daily using the HESAI HS4000 (Hesai, Building L2-B, Hongqiao World Centre, Shanghai) laser methane detector. Methane concentrations were measured as CH₄ column density (ppm) at a specified time, two hours after feeding to account for diurnal fluctuations. Critical peripartum phases (prepartum, parturition, and postpartum) were chosen for observation to document notable physiological alterations. Weekly blood samples from the coccygeal vein were obtained for metabolic analysis, yielding extensive data on bovine health, behaviour, and methane emissions during this transitional phase. Results: The result of our study reveals a trend of increased methane emissions in cows on the day of calving, although variations across the transition periods were not statistically significant. Methane concentrations increased by 30.890 ppm on calving day relative to three weeks prior and by 13.597 ppm three weeks post­ calving (p > 0.05). In the pre­ calving period, methane emissions exhibited a mild positive correlation with Other Chews time (r = 0.410, p < 0.01) and a negative correlation with Chews per Bolus (r = −0.306, p < 0.05). Methane emissions exhibited significant correlations with blood morphology over time: a positive correlation with monocytes prior to calving (r = 0.501, p < 0.01), a negative correlation with platelet counts on the day of calving (r = -0.641, p < 0.05), and post­ calving, negative correlations with platelets (r = -0.413, p < 0.01), alongside a positive correlation with haematocrit (r = 0.413, p < 0.01). Conclusions: This study indicates a propensity for increased methane emissions in dairy cows during the calving period, despite the absence of statistically significant differences across transition periods. Significant correlations with physiological and behavioural indicators, such as monocyte and platelet levels, underscore the metabolic changes that cows experience during this period, which may influence methane emissions. However, the limited sample size requires further investigation with a larger cohort to validate these results. Observing cows during the peripartum period may facilitate methane reduction efforts and improve animal welfare by reducing metabolic stress, potentially leading to a decrease in greenhouse gas emissions in dairy farming.