Impact of methane-mitigating concentrate feed on milk production, composition, and udder health in Holstein cows.

Enteric methane emissions from dairy cattle contribute substantially to agricultural greenhouse gas output. Although feed-based mitigation strategies have shown promise in controlled research environments, their effects under commercial farm conditions remain insufficiently studied. This field-based study evaluated the associations between methane-mitigating concentrate (MM) feed and milk yield, milk composition, and udder health indicators in Holstein cows across three commercial farms in Jeju, South Korea. A total of 400 lactating cows were monitored over 47 months (January 2021–November 2024) as the farms transitioned from conventional concentrate feed to MM feed. Mixed models and stepwise regression analyses were used to assess the independent effects of MM feeding while accounting for farm, parity, and seasonal variation. MM feeding did not significantly affect overall milk yield or milk fat content. However, MM feeding was associated with lower milk protein, solid non-fat (SNF), and milk urea nitrogen (MUN) concentrations, along with a modest increase in somatic cell count (SCC). These associations varied among farms and parities, indicating that the effects of MM feed are influenced by management and physiological factors rather than a single dietary component. Stepwise regression retained MM feeding as a significant explanatory variable for SNF, MUN, and SCC, but not for milk yield or fat content. These findings indicate that MM feed can be implemented under commercial farm conditions without compromising milk yield, while influencing nitrogen-related milk traits and udder health indicators. Further studies incorporating direct methane measurements and mechanistic evaluation of rumen fermentation and nitrogen utilization are needed to determine the environmental implications of MM feeding.