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Relationship of Pulsation Rate, Pulsation Ratio, and Vacuum Decrease Time to Milking Performance¹

Department of Animal Science

D. A. Dickey

Department of Statistics, North Carolina State University, Raleigh 27650

ABSTRACT

Pulsation rate, pulsation ratio, and vacuum-decrease time were regulated independently and applied in various combinations to individual quarters of four experimental cows. A static pulsation ratio was used in assigning treatments and was measured on pulsation curves at 20 kPa. This was the vacuum at which liner walls parted during graduated pressure adjustment. A dynamic pulsation ratio also was measured for the actual point at which liner walls first separated or first touched during each pulsation cycle. Vacuum-decrease time was defined as the period starting with decreasing vacuum in the pulsation chamber and ending when ambient pressure was reached. Pulsation rates of 35, 50, 65, and 80/min; static ratios of 40:60, 50:50, 60:40, and 70:30; and vacuum-decrease times of .26, .16, and .06 s were studied for four Holstein cows. Teat end vacuum was 42.3 kPa. Increasing pulsation rate from 35 to 50/min or increasing static ratio increased peak and average milking rates and decreased machine and total milking times. Changing vacuum-decrease time or increasing pulsation rate from 50 to 65 or 80/min had no effect on milking. Stripping yield increased as static ratio increased, but this effect was not large enough to be practically important. There was no effect of pulsation rate, static ratio, or vacuum-decrease time on milk or fat yield. No interactions among these pulsation characteristics were found.

¹ Paper No. 6936 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh. Use of trade names in this publication does not imply endorsement of the products mentioned.