The bovine teat canal: information from measurement of velocity of milk flow from the teat.

The velocity of milk flow from the teat during the peak flow rate period of milking was estimated to be approximately 8.5 m/s with a liner vacuum of 50 kPa and 7.5 m/s at 40 kPa. These results confirm the applicability of the Bernoulli theorem for estimating velocity of milk flow through the teat canal during milking. Concurrent measurements of mass flow rate and velocity indicate that the effective diameter of the open teat canal is approximately 2 mm. Further calculations indicate that the shear force due to milk flow acting to debride the surface of the open teat canal is about 1.8 X 10(-2) N. The opposing surfaces of the 'closed' teat canal may be approximately 100 micron apart immediately after milking. If so, bacteria present in the milk residue within the teat canal would never be more than 50 micron from a surface.