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Air Leakage Past the Teat and Teatcup Liner During Milking

Authors: G.A. Mein, C.C. Thiel, Rosemary J. Fulford and J.B. Hoyle

Abstract:

Calculations based on measurements of the pressure and volume changes in the mouth-piece chambers of different liners indicated that small amounts of air normally leak past the teat during milking. Because these calculated values were necessarily regarded as minimum rates, direct measurements of the amount of air leaking past the teats of 8 cows milked with 4 makes of liners were made under conditions of both fast and slow rates of liner movement. The liners were assembled in separate, independent teatcup assemblies and also in conventional clusters. The overall mean rates of air leakage measured while the teatcups were stable on the cow were: 0.2 litre/min of free air per cluster during the period of peak milk flowrate; 0.8 1/min early in the period of reduced milk flowrate and 0.4 1/min at the end of this period. With each of the liners there were frequent measuring intervals during which no air leaked past the teat.

The measured air leakage rates were similar to the values calculated from pressure and volume changes in the mouthpiece chamber. This similarity implied that air normally leaked past the teat and mouthpiece lip, and then past the teat and barrel, during separate phases of a pulsation cycle. Records of mouthpiece chamber vacuum also supported this conclusion, indicating that air entered the chamber as the liner closed and passed down between the teat and barrel of the liner as it opened.

$15.00 (inc. GST)