Abstract
Cisternal milk evaluation by direct udder scanning ultrasonography was applied in two experiments in dairy cows. In Experiment 1, alveolar and cisternal milk volumes (by cannula) and cisternal area (by ultrasonography) were measured in the front udder quarters, 12 h after milking, in 18 dairy cows. Cisternal milk and cisternal area correlated for pooled data and lactation stage grouped data (r = 0.74 to 0.82; P < 0.01). As lactation stage progressed, volumes of alveolar and cisternal milk, and cisternal area decreased. In Experiment 2, cisternal area of fore quarters was evaluated by ultrasonography for an interval of 7 to 10 h after milking in 30 dairy cows. Cows were divided into three groups according to initial cisternal size, then 5 min after inducing milk letdown by an i.m. oxytocin (OT) injection they were scanned again to evaluate their maximum cistern distension. Area of cistern increased dramatically after OT injection and significant (P < 0.01) correlations were observed between milk yield and cisternal area before (r = 0.65) and after (r = 0.68) the OT injection. In conclusion, ultrasonography was a useful method to evaluate size and dynamic changes in cisternal milk throughout lactation.