Blood perfusion of teat tissue in dairy cows: Changes associated with pre-milking stimulation and machine milking

摘要

Mechanical forces during machine milking of dairycows evoke circulatory impairment of the teat tissuethat may affect the teats’ defense mechanisms againstmastitis pathogens. Ample research describes dimensionalchanges of different teat traits after machinemilking, whereas reports that describe changes in bloodcirculation of dairy cows’ teats are limited. Therefore,the objectives of this study were to (1) describe changesin teat blood circulation that occur after pre-milkingteat stimulation and machine milking and (2) study theeffect of 2 different milking liners on machine milkinginducedchanges in teat blood flow. In a randomizedtrial, Holstein dairy cows were stratified by parity,stage of lactation, and average daily milk yield duringthe previous week, and allocated to 1 of 2 treatmentgroups. Treatment consisted of 1 milking observationwith either a round or multisided concave milking liner.Teat scans were taken of the left front and the right hindteats using power Doppler ultrasonography. Imaging occurredbefore pre-milking udder preparation (T1), aftercompletion of pre-milking udder preparation but beforemilking-unit attachment (T2), and immediately afterunit detachment (T3). Perfusion intensity measurementsfrom teat scans were performed with a commerciallyavailable software program. Data from 109 cowswere analyzed. A general linear mixed model showeddifferences 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 betweentreatment groups were observed. We conclude thatteat 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 magnitudeof their influence and to further our understanding ofhow these changes relate to the susceptibility to intramammaryinfection and milking performance.