Udder Capacity Estimates as Affected by Rate of Milk Secretion and Intramammary Pressure

Abstract

An extra-period Latin-square design balanced for sequence effects, with 4 groups of 5 Jersey dairy cows per group, was used to study udder capacity. A group of 5 Brown Swiss provided additional information. Experimental milking intervals were 8, 12, 16, 20, and 24 hours in length. The effects of the preceding milking interval had no influence on experimental milking intervals. Sequence effects were not significant. Oxytocin (20 International Units) was injected before and after each experimental interval to eliminate residual milk effects. With increasing milking intervals the total pounds of milk increased asymptotically for all groups. The estimated theoretical udder capacities for the 5 groups of cows were 42.4, 49.9, 55.8, 51.3, and 63.2 lb. of milk. Thirty-five hours was the estimated time before milk secretion approached zero. Increases in total milk increased the intramammary pressure. With increases in milking interval, total milk, and/or intramammary pressure, both average and instantaneous secretion rates declined.