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The Effect of Increasing the Negative Pressure and Widening of the Vacuum-Release Ratio on the Rate of Removal of Milk from the Udder^1,2,

University of Minnesota

ABSTRACT

1. Data involving observations on 12 cows are presented to show the effects of increasing the negative pressures and widening the pulsation ratios upon the rates of milk flow and the completeness of milking.
   
2. Rates of milk withdrawal at the height of milking were established for 1 minute at 10, 12.5 and 15 inches Hg negative pressures and rates per 10 seconds for the 1:1 and 3:1 pulsation ratios at 10, 12 and 14 inches Hg and for the 1:1 and 2:1 pulsation ratios at 10, 12, 14 and 16 inches Hg negative pressure levels.
   
3. Each increment in negative pressure in the range of 10 to 16 inches Hg, increased the rate of milk withdrawal but not at uniform rates for all cows.
   
4. Widening the pulsation ratio increased the rate of milk withdrawal but not in proportion to the increased time of vacuum application.
   
5. In general there was lesser increase in the rate of milk withdrawal by the wider pulsation ratios as the negative pressures increased.
   
6. The effect of negative pressure and widening of the pulsation ratios upon the completeness of milking was variable. In the lower ranges increased negative pressure affected a more complete average evacuation of the gland at the "end point." At 16 inches Hg negative pressure the reverse maintained.
   
7. Shape of the udder contributes to completeness of milking. Funnel-shaped quarters milk out less completely than those where the udder floor is level.
   

¹ Paper No. 2253, Scientific Journal Series, Minn. Agr. Expt. Station.

² The data in this paper are taken from a thesis presented by Vearl E. Smith in partial fulfillment of the requirements for the degree of Doctor of Philosophy, University of Minnesota.