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Retrograde Flow of Milk Within Machine-Milked Teats

United States Department of Agriculture, Animal Physiology & Genetics Institute, ARD, BARC, Beltsville, MD 20705

ABSTRACT

Milk flow velocity within machine-milked teats was measured with a Doppler ultrasonic velocity meter probe inserted in the mouthpiece of the teat-cup liner. A reflux of milk from the teat into the gland cistern consistently accompanied each contraction of the liner. Such reflux may provide a mechanism for the transmission of pathogens from teat into gland cistern during milking. For 77 observations, the mean reflux, estimated by the areas under the reverse flow velocity curve, was 34% of the forward flow within each pulsation cycle. Measurement of vacuum inside the teat-cup liner revealed an increase of vacuum fluctuation with greater milk flow and with lack of admission of air to the short milk tube.