Prepartum milk leakage happens in some pregnant dairy cows close to calving. It has been hypothesized that low blood Ca is a cause of this event. To investigate the possible reason(s) of milk leakage, 137 multiparous pregnant Holstein cows were enrolled in the experiment and categorized by the presence (72 heads; leak group) or lack (65 heads; control group) of milk leakage before calving. The concentrations of Ca and P and the length of the teat were measured for all cows. Data showed that Ca concentration was not different between cows in the leak group (7.90 mg/dL) and those in the control group (7.99 mg/dL). Moreover, neither P concentration (4.62 vs. 4.54 mg/dL) nor teat length (4.28 vs 4.10 cm) differed between leak and control groups. Milk yield was greater for the leak group (53.6 kg/d) compared with the control group (50.1 kg/d) through 4 mo in milk. The leakage did not affect the odds of postpartum disorders such as retained placenta, metritis, mastitis, displaced abomasum, or lameness occurrence. The current results show that hypocalcemia is not a reason for observed prepartum leakage and that cows in the leak group produced more milk in the subsequent lactation period.
