Negative effects of overmilking on mastitis in dairy cows

Overmilking (OVM)—the continuation of the milking process after milk flow has ceased—is a common issue in dairy management. Prolonged overmilking adversely affects udder health, but the threshold duration for significant impact remains undefined. This study, therefore, aims to assess the impact of varying overmilking durations on somatic cell count (SCC), milk yield, incidence of clinical mastitis (CM), lactation stage, days in milk (DIM), and the relationship between teat-end vacuum duration (i.e., overmilking or idle milking time) and the occurrence of bacterial intramammary infections, to provide practical insights to improve milking practices on dairy farms. This study used Vadia Biocontrol devices with milk point controllers (MPC) to monitor Holstein-Friesian cows on three farms, recording and categorizing overmilking durations, particularly those exceeding 240 seconds. Milk samples were analyzed for SCC and cases of clinical mastitis were documented. Additional data on milk yield, lactation stage, and DIM were also collected and analyzed in order to evaluate the broader impact of overmilking. The study found that overmilking for longer than 240 seconds had a statistically significant (p < 0.05) negative effect on udder health. However, the study found that extended overmilking did not contribute to a higher incidence of bacterial intramammary infections.