Upton J, Penry J F, Rasmussen M D, Thompson P D, Reinemann D J
Animal and Grassland Research and Innovation Centre, Teagasc Moorepark, Fermoy, Co. Cork, Ireland.
Department of Dairy Science, University of Wisconsin, Madison 53706.
J Dairy Sci. 2016 May;99(5):3958-3965. doi: 10.3168/jds.2015-10466.
The objective of this study was to quantify the effect of d-phase (rest phase) duration of pulsation on the teat canal cross-sectional area during the period of peak milk flow from bovine teats. A secondary objective was to test if the effect of d-phase duration on teat canal cross-sectional area was influenced by milking system vacuum level, milking phase (b-phase) duration, and liner overpressure. During the d-phase of the pulsation cycle, liner compression facilitates venous flow and removal of fluids accumulated in teat-end tissues. It was hypothesized that a short-duration d-phase would result in congestion of teat-end tissue and a corresponding reduction in the cross-sectional area of the teat canal. A quarter milking device, designed and built at the Milking Research and Instruction Laboratory at the University of Wisconsin-Madison, was used to implement an experiment to test this hypothesis. Pulsator rate and ratios were adjusted to achieve 7 levels of d-phase duration: 50, 100, 150, 175, 200, 250, and 300ms. These 7 d-phase durations were applied during one milking session and were repeated for 2 vacuum levels (40 and 50kPa), 2 milking phase durations (575 and 775ms), and 2 levels of liner overpressure (9.8 and 18kPa). We observed a significant reduction in the estimated cross-sectional area of the teat canal with d-phase durations of 50 and 100ms when compared with d-phase durations of 150, 175, 225, 250, and 300ms. No significant difference was found in the estimated cross-sectional area of the teat canal for d-phase durations from 150 to 300ms. No significant interaction was observed between the effect of d-phase and b-phase durations, vacuum level, or liner overpressure.
本研究的目的是量化在奶牛乳头产奶高峰期，脉动d阶段（静止阶段）的持续时间对乳头管横截面积的影响。第二个目的是测试d阶段持续时间对乳头管横截面积的影响是否受挤奶系统真空度、挤奶阶段（b阶段）持续时间和内衬超压的影响。在脉动周期的d阶段，内衬压缩有助于静脉血流，并清除乳头末端组织中积聚的液体。据推测，d阶段持续时间较短会导致乳头末端组织充血，并相应减少乳头管的横截面积。使用威斯康星大学麦迪逊分校挤奶研究与教学实验室设计并制造的四分之一挤奶装置进行实验，以验证这一假设。调整脉动器速率和比率，以实现7种d阶段持续时间：50、100、150、175、200、250和300毫秒。在一次挤奶过程中应用这7种d阶段持续时间，并针对2种真空度（40和50千帕）、2种挤奶阶段持续时间（575和775毫秒）和2种内衬超压水平（9.8和18千帕）重复进行。与d阶段持续时间为150、175、225、250和300毫秒相比，我们观察到d阶段持续时间为50和100毫秒时，乳头管的估计横截面积显著减小。d阶段持续时间在150至300毫秒之间时，乳头管的估计横截面积未发现显著差异。在d阶段和b阶段持续时间、真空度或内衬超压的影响之间未观察到显著的相互作用。
