Abstract
During the phase of evacuation five different vacuum patterns were applied in a linerless experimental cup. The patterns show a normal distribution, a triangle, a four-corner pulse, a left-wing trapezoid and a right-wing peak trapezoid. All patterns had a maximal vacuum of 35 and an average vacuum level of 12 kPa. Evacuation phases lasted from 4.3 to 6.9 s and were followed by varying atmospheric phases so that evacuation was started repeatedly with a frequency of 0.09 Hz for all patterns. The patterns differed mainly in the mode of pressure change and in the length of the period of almost maximum vacuum. Both the fourcorner pulse and the normal distribution pattern showed satisfying milking efficiency but seemed to differ in their fitness for slow or fast milking cows. The results generally support the hypotheses of different vacuum functions and biologically influenced thresholds for these functions.