Department of Dairy Science, University of Wisconsin-Madison, Madison 53706.
Animal and Grassland Research and Innovation Centre, Teagasc Moorepark, Fermoy, Co. Cork, Ireland P61P302.
J Dairy Sci. 2018 Jan;101(1):649-660. doi: 10.3168/jds.2017-12942. Epub 2017 Nov 6.
The objective of this study was to develop a method to quantify the milking conditions under which circulatory impairment of teat tissues occurs during the peak flow period of milking. A secondary objective was to quantify the effect of the same milking conditions on milk flow rate during the peak flow rate period of milking. Additionally, the observed milk flow rate was a necessary input to the calculation of canal area, our quantitative measure of circulatory impairment. A central composite experimental design was used with 5 levels of each of 2 explanatory variables (system vacuum and pulsator ratio), creating 9 treatments including the center point. Ten liners, representing a wide range of liner compression (as indicated by overpressure), were assessed, with treatments applied using a novel quarter-milking device. Eight cows (32 cow-quarters) were used across 10 separate evening milkings, with quarter being the experimental unit. The 9 treatments, with the exception of a repeated center point, were randomly applied to all quarters within each individual milking. Analysis was confined to the peak milk flow period. Milk flow rate (MFR) and teat canal cross sectional area (CA) were normalized by dividing individual MFR, or CA, values by their within-quarter average value across all treatments. A multiple explanatory variable regression model was developed for normalized MFR and normalized CA. The methods presented in this paper provided sufficient precision to estimate the effects of vacuum (both at teat-end and in the liner mouthpiece), pulsation, and liner compression on CA, as an indicator of teat-end congestion, during the peak flow period of milking. Liner compression (as indicated by overpressure), teat-end vacuum, vacuum in the liner mouthpiece, milk-phase time, and their interactions are all important predictors of MFR and teat-end congestion during the peak milk flow period of milking. Increasing teat-end vacuum and milk-phase time increases MFR and reduces CA (indicative of increased teat-end congestion). Increasing vacuum in the liner mouthpiece also acts to reduce CA and MFR. Increasing liner compression reduces the effects of teat-end congestion, resulting in increased MFR and increased CA at high levels of teat-end vacuum and milk-phase time. These results provide a better understanding of the balance between milking speed and milking gentleness.
本研究的目的是开发一种方法来量化挤奶过程中在高峰期奶流期间发生的乳腺组织挤奶条件。次要目的是量化相同挤奶条件对高峰期奶流率的影响。此外，观察到的奶流率是计算我们对循环障碍的定量测量——奶管区域的必要输入。采用中心复合实验设计，每个解释变量（系统真空和脉动器比率）有 5 个水平，创建 9 种处理方法，包括中心点。使用一种新型四分之一挤奶装置评估了 10 个衬垫，这些衬垫代表了广泛的衬垫压缩范围（如超压所示），处理方法应用于 10 个单独的晚间挤奶。8 头奶牛（32 个奶牛乳房）在 10 次单独的挤奶中使用，每个乳房为一个实验单位。除了重复的中心点外，9 种处理方法随机应用于每个个体挤奶中的所有乳房。分析仅限于高峰期奶流期。通过将个体 MFR 或 CA 值除以所有处理的跨季度平均值，将奶流率（MFR）和奶管横截面积（CA）标准化。建立了一个用于标准化 MFR 和标准化 CA 的多解释变量回归模型。本文提出的方法提供了足够的精度来估计真空（在乳腺末端和衬垫口中）、脉动和衬垫压缩对 CA 的影响，CA 是乳腺末端充血的指标，在挤奶高峰期。衬垫压缩（如超压所示）、乳腺末端真空、衬垫口中的真空、奶相时间及其相互作用都是挤奶高峰期 MFR 和乳腺末端充血的重要预测因素。增加乳腺末端真空和奶相时间会增加 MFR 并降低 CA（表明乳腺末端充血增加）。增加衬垫口中的真空也会降低 CA 和 MFR。增加衬垫压缩会降低乳腺末端充血的影响，从而在乳腺末端真空和奶相时间较高时增加 MFR 和增加 CA。这些结果更好地理解了挤奶速度和挤奶温和性之间的平衡。
