Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853.
Department of Animal Science, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853.
J Dairy Sci. 2020 Jul;103(7):6588-6599. doi: 10.3168/jds.2020-18219. Epub 2020 May 7.
Mechanical forces during machine milking of dairy cows evoke circulatory impairment of the teat tissue that may affect the teats' defense mechanisms against mastitis pathogens. Ample research describes dimensional changes of different teat traits after machine milking, whereas reports that describe changes in blood circulation of dairy cows' teats are limited. Therefore, the objectives of this study were to (1) describe changes in teat blood circulation that occur after pre-milking teat stimulation and machine milking and (2) study the effect of 2 different milking liners on machine milking-induced changes in teat blood flow. In a randomized trial, Holstein dairy cows were stratified by parity, stage of lactation, and average daily milk yield during the previous week, and allocated to 1 of 2 treatment groups. Treatment consisted of 1 milking observation with either a round or multisided concave milking liner. Teat scans were taken of the left front and the right hind teats using power Doppler ultrasonography. Imaging occurred before pre-milking udder preparation (T1), after completion of pre-milking udder preparation but before milking-unit attachment (T2), and immediately after unit detachment (T3). Perfusion intensity measurements from teat scans were performed with a commercially available software program. Data from 109 cows were analyzed. A general linear mixed model showed differences in perfusion intensity between time points. Least squares means (95% confidence intervals) for T1, T2, and T3, respectively, were 0.035% (0.026-0.047), 0.124% (0.093-0.164), and 0.095% (0.073-0.124). Conversely, no statistically significant differences between treatment groups were observed. We conclude that teat blood circulation is subjected to several influences, including inherent circulatory regulation mechanisms, as well as extrinsic factors such as machine milking. Future research is warranted to decipher the magnitude of their influence and to further our understanding of how these changes relate to the susceptibility to intramammary infection and milking performance.
奶牛机械挤奶过程中的机械力会引起乳头组织的循环障碍，这可能会影响乳头的防御机制，使其抵抗乳腺炎病原体。大量研究描述了机械挤奶后不同乳头特征的尺寸变化，而描述奶牛乳头血液循环变化的报道则有限。因此，本研究的目的是：（1）描述预奶刺激和机械挤奶后乳头血液循环的变化；（2）研究 2 种不同挤奶衬垫对机械挤奶引起的乳头血流变化的影响。在一项随机试验中，荷斯坦奶牛按胎次、泌乳阶段和前一周的平均日产量进行分层，然后分配到 2 个处理组中的 1 个。处理包括 1 次挤奶观察，使用圆形或多边凹形挤奶衬垫。使用功率多普勒超声对左前乳头和右后乳头进行乳头扫描。扫描在预挤奶前的乳房准备（T1）、预挤奶前的乳房准备完成但在挤奶装置连接之前（T2）和装置脱开后立即（T3）进行。使用商业上可用的软件程序对乳头扫描的灌注强度测量进行分析。对 109 头牛的数据进行了分析。一个一般线性混合模型显示了不同时间点之间的灌注强度差异。T1、T2 和 T3 的最小二乘均值（95%置信区间）分别为 0.035%（0.026-0.047）、0.124%（0.093-0.164）和 0.095%（0.073-0.124）。相反，处理组之间没有观察到统计学上的显著差异。我们得出结论，乳头血液循环受到多种因素的影响，包括内在的循环调节机制以及机械挤奶等外在因素。未来的研究需要阐明它们的影响程度，并进一步了解这些变化与乳腺炎易感性和挤奶性能的关系。
