Influence of postpartum disorders, parity, and season on estimated methane emissions in dairy cows in northwest of Spain.

This study evaluated the influence of postpartum disorders, parity, stage of lactation, and season on estimated enteric methane emissions in dairy cows from northwestern Spain using dairy herd improvement (DHI) data. A total of 2,440 lactating Holstein cows from 50 commercial dairy farms were included. Data from four official monthly DHI controls conducted in 2017 included daily milk yield, milk composition, parity, and postpartum disorders recorded within 21 days in milk. Methane emissions (MEE; g CH₄/day) were estimated using a prediction equation based on energy-corrected milk, and methane emission intensity (MEEI) was calculated as g CH₄/kg of daily milk yield. MEEI was highest in early lactation and declined as milk yield increased. Retained placenta, metritis, subclinical mastitis, and abomasal displacement were associated with higher MEEI, whereas ketosis was associated with higher milk yield and total MEE but not with MEEI. Multiparous cows had higher total MEE but lower MEEI than primiparous cows. During warm months, cows produced less milk and had lower total MEE but higher MEEI than during cold months. These findings indicate that DHI-based methane estimates can be used as practical indicators of emission efficiency in dairy herds. Differences in methane intensity were mainly associated with milk production efficiency and were influenced by health status, parity, lactation stage, and season. Improving early-lactation health and reducing seasonal stress may help lower methane emissions per unit of milk, although direct methane measurements are needed to validate these estimates. Future studies should validate these estimates using direct on-farm methane measurements.