Vacuum Dynamics as an Alternative Method for Detection of Bimodal Milk Ejection in Dairy Cows

The primary objective of our study was to assess the ability of a vacuum recorder to detect the presence of bimodal milk flow curves in dairy cows compared with a portable milk flow meter. In a cross-sectional study, 241 individual cow milking observations were analyzed. We simultaneously collected (1) individual cow vacuum events during milking using portable vacuum recorders, and (2) individual cow milk flow curves by attaching a portable milk flow meter to the same milking unit. Presence of bimodality was assessed with the vacuum recorder visually (BIM_VA) and with the gold standard method of a milk flow meter through automatic detection (BIM_LA). Kappa statistics revealed moderate agreement between BIM_VA and BIM_LA [κ, 95% confidence intervals (95% CI) = 0.59 (0.46-0.71)]. Diagnostic test statistics for BIM_VA for detection of bimodality indicated moderate performance for sensitivity [0.65 (0.52-0.76)] and positive predictive value [0.71 (0.58-0.82)] and high values for specificity [0.92 (0.87-0.95)] and negative predictive value [0.93 (0.84-0.93)]. We conclude that milking vacuum dynamics are a suitable measure to assess bimodal milk flow curves in dairy cows.