Effect of Duration of Teat Cup Liner Closure Per Pulsation Cycle on Bovine Mastitis

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Abstract
Measurements of teat end expansion and contraction times from step changes in pressure suggest that teat ends require a minimal duration of liner closure for response. Effect of duration of liner closure per pulsation cycle on susceptibility of the udder to infection was tested. Four durations of liner closure (liner > 1/2 closed) were applied: 0, 0.17, 0.34 and 0.51 s/pulsation cycle. For the latter 3 treatments, duration of the liner > 1/2 open was .66 s/pulsation cycle, resulting in pulsation rates of 72.3, 60.0 and 51.3 pulsations/min. Four groups, each of 10 British Friesian cows, were in a 4-wk experiment. High bacterial exposure of all teats was ensured by dipping them before and after each milking in a suspension of Streptococcus agalactiae and S. dysgalactiae. Numbers of quarters becoming infected/treatment group were 20, 11, 4 and 5. This result represents both a significant inverse linear and quadratic relationship between proportion of quarters becoming infected and duration of liner closure. A sufficient duration of liner closure, i.e., 1/3 of a second or more, per pulsation cycle contributes to reducing risk of new mammary gland infections.