Impact of claw lesions on dairy cow energy-corrected milk yield: Differential and persistent effects up to 120 days post-treatment

Claw lesions can substantially reduce milk production in dairy cows, yet quantification by lesion type and disease phase is limited. We analysed 5,947 daily milk yield records from 818 cows to evaluate the impact of specific claw lesions on energy-corrected milk (ECM), considering lesion type and disease phases (pre-treatment, treatment, post-treatment). Mixed linear models revealed significant effects of the diagnosis × phase interaction (<i>P</i><0.001) and lactation order (<i>P</i><0.001). Healthy cows maintained a stable LS Mean ECM of 33.91±0.19 kg/day. The largest production loss occurred in interdigital phlegmon during treatment (reduction of 4.8 kg/day relative to healthy cows). Reductions were also observed in digital dermatitis (DD), white line disease (WL), sole ulcer (SU), toe ulcer (TU), and combination lesions, with persistent deficits for some claw horn lesions post-treatment (e.g., SU: <i>β</i>=-1.9, <i>P</i>=0.05). A significant pre-treatment elevation in ECM observed for white line disease (+2.4 kg/day) likely reflects the higher baseline production and increased susceptibility of these individuals to claw lesions, rather than a beneficial effect of the pre-clinical disease phase. These findings highlight the importance of early detection, effective treatment, and preventive claw trimming and claw care to maintain milk production, minimise economic losses, and ensure animal welfare. Interpretive Summary: We evaluated how specific claw lesions influence milk production across disease phases using daily records. Milk output typically fell during treatment and partially recovered post-treatment. However, several claw-horn lesions exhibited more durable deficits, suggesting lingering effects beyond clinical resolution. The pattern indicates that some conditions cause a brief, acute production loss, whereas others impose longer-lasting penalties. These insights support earlier recognition, targeted therapy, and preventive management-claw trimming, flooring, cow flow, and comfort-to maintain yield, limit economic losses, and improve welfare.