ABSTRACT
The main machine milking factors investigated in relation to mastitis were vacuum level, pulsation rate, pulsator ratio, liner bore, and overmilking. The level of infection in a herd at any time is determined by the duration of infection and the rate of new infection. Since the duration of most infections is long, the rate of new infection is a major determinant of infection levels. An Irish farm survey showed a significant negative regression of bulk milk cell count on the vacuum reserve of the milking plant. A series of experiments of the NIRD, Reading, showed that large irregular fluctuations or large cyclic fluctuations per se did not increase new infection rates. In the experiments, airblasts occurred just after the liner was fully opened in the pulsation cycle. Pulsators with small extraction capacities may give unsatisfactory graphs with long liners; it is always necessary to check the pulsation graphs.
