Effect of pulsation rest phase duration on teat end congestion

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 d-phase 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 300ms. These 7 d-phase durations were applied during one milking session and were repeated for 2 vacuum levels (40 and 50kPa), 2 milking phase durations (575 and 775ms), and 2 levels of liner overpressure (9.8 and 18kPa). We observed a significant reduction in the estimated cross-sectional area of the teat canal with d-phase durations of 50 and 100ms when compared with d-phase durations of 150, 175, 225, 250, and 300ms. No significant difference was found in the estimated cross-sectional area of the teat canal for d-phase durations from 150 to 300ms. No significant interaction was observed between the effect of d-phase and b-phase durations, vacuum level, or liner overpressure.

Short communication: Teat-end shape and udder-level milking characteristics and their associations with machine milking-induced changes in teat tissue condition

“…Short-term changes represent tissue responses to a single milking and are due to congestion and edema (Hamann and Mein, 1990;Mein et al, 2001;Ohnstad et al, 2007). They have been associated with teat canal openness, penetrability, and thus susceptibility to new IMI Paulrud et al, 2005;Upton et al, 2016) and diminished animal well-being (Hillerton et al, 2002). Multiple researchers therefore have been investigating short-term changes using various techniques including radiography (McDonald, 1968(McDonald, , 1975, ultrasonography Weiss et al, 2004;Ambord and Bruckmaier, 2010), thermography (Paulrud et al, 2005), a modified skin-fold caliper (Hamann and Mein, 1988;Hamann et al, 1993), and visual assessment using a standardized scoring system that is based on discoloration of the teat skin, condition of the teat base and end, and appearance of the teat orifice (Hillerton et al, 2000).…”

Machine milking–induced changes in teat canal dimensions as assessed by ultrasonography

“…Sustaining teat canal integrity and pliability of its adjacent tissues is therefore critical to resist IMI (O'Shea, 1987;Mein, 2012). It is generally agreed that machine milking induces changes (long-, medium-, and short-term) in teat canal integrity and tissue pliability (Neijenhuis et al, 2001a;Upton et al, 2016;Penry et al, 2017). Long-term changes in teat condition are the adaptation of teat tissue to machine milking over many weeks and include the degree of teat end callosity thickness and teat end callosity roughness (Neijenhuis et al, 2000).…”

Short communication: Cow- and quarter-level milking indicators and their associations with clinical mastitis in an automatic milking system

“…In all the referenced studies examining the association of either high UPMF or QPMF with increased risk of CM, no authors proposed a causal pathway to disease as a result of high milk flow rate. Under constant milking system vacuum and pulsation, increased QPMF results from an increase in teat-end canal cross-sectional area (Upton et al, 2016). Underlying thinking behind a potential causal link may have been that, because the teat canal was wider during milk flow, bacterial entry was more probable under conditions where reverse flow milk droplets affected the teat end.…”