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 milkinginduced 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.

Ample research has described the assessment of dimensional changes for different teat traits, whereas diagnostic techniques to reliably assess blood circulation in teats of dairy cows are limited. Here, we describe the development and evaluation of a scanning technique to quantify blood flow in teats of dairy cows using power Doppler ultrasonography. In 2 consecutive trials, 384 teat scans [trial 1, n = 256 (sagittal plane, n = 128; transverse plane, n = 128); trial 2, n = 128 (transverse plane)] from 16 cows were obtained by the same 2 operators. Perfusion intensity from single images (trial 1) and video images (trial 2) were assessed using a commercially available software program. Intraclass correlation coefficients (ICC) and concordance correlation coefficients (CCC) were used to assess interoperator reproducibility (agreement between measurements performed by different operators) and intraoperator repeatability (agreement between measurements performed by the same operator). In trial 1, interoperator ICC and CCC indicated poor agreement (ICC ≤0.26, CCC ≤0.26). Intraoperator ICC and CCC demonstrated poor agreement between duplicate measurements within operators (ICC ≤0.19, CCC ≤0.19). Modifications after trial 1 included (1) a different ultrasound device, (2) analysis of video clips rather than single images, (3) restriction to 1 sectional plane (i.e., transverse), and (4) a scanning sequence such that repeated scans within operators were measured one after another. Through these modifications, intraoperator repeatability in trial 2 yielded fair to good agreement, with intraoperator ICC and CCC over both operators ranging from 0.44 to 0.70 and from 0.57 to 0.69, respectively, whereas interoperator ICC and CCC showed poor agreement (ICC = 0.35, CCC = 0.34). We conclude that repeatable measurements of blood perfusion intensity of teats in dairy cows can be attained with power Doppler ultrasonography. Power Doppler ultrasonography is a suitable tool to quantify slow flow in small vessels and may be an acceptable diagnostic technique to assess changes in blood circulation that result from machine milking in teats of dairy cows, although further research is necessary to validate this hypothesis.

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