J. Dairy Sci. 99:3958–3965 http://dx.doi.org/10.3168/jds.2015-10466 © American Dairy Science Association®, 2016.
Effect of pulsation rest phase duration on teat end congestion
J. Upton,*1 J. F. Penry,† M. D. Rasmussen,‡ P. D. Thompson,§ and D. J. Reinemann§
*Animal and Grassland Research and Innovation Centre, Teagasc Moorepark, Fermoy, Co. Cork, Ireland †Department of Dairy Science, University of Wisconsin, Madison 53706 ‡Aarhus University, Department of Engineering, DK-8000 Aarhus C, Denmark §Biological Systems Engineering Department, University of Wisconsin, Madison 53706
ABSTRACT The objective of this study was to quantify the effect of d-phase (rest phase) duration of pulsation on the teat canal cross-sectional area during the period of peak milk flow from bovine teats. A secondary objective was to test if the effect of d-phase duration on teat canal cross-sectional area was influenced by milking system vacuum level, milking phase (b-phase) duration, and liner overpressure. During the d-phase of the pulsation cycle, liner compression facilitates venous flow and removal of fluids accumulated in teat-end tissues. It was hypothesized that a short-duration dphase would result in congestion of teat-end tissue and a corresponding reduction in the cross- sectional area of the teat canal. A quarter milking device, designed and built at the Milking Research and Instruction Laboratory at the University of Wisconsin–Madison, was used to implement an experiment to test this hypothesis. Pulsator rate and ratios were adjusted to achieve 7 levels of d-phase duration: 50, 100, 150, 175, 200, 250, and 300 milli-seconds (ms). These 7 d-phase durations were applied during one milking session and were repeated for 2 vacuum levels (40 and 50 kPa), 2 milking phase durations (575 and 775 ms), and 2 levels of liner overpressure (9.8 and 18 kPa). We observed a significant reduction in the estimated cross-sectional area of the teat canal with d-phase durations of 50 and 100 ms when compared with d-phase durations of 150, 175, 225, 250, and 300 ms. No significant difference was found in the estimated cross-sectional area of the teat canal for d-phase durations from 150 to 300 ms. No significant interaction was observed between the effect of d-phase and b-phase durations, vacuum level, or liner overpressure.
Key words: milking, pulsation, teat congestion, milk flow.
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