Measurement of machine-induced changes in thickness of the bovine teat

Abstract

Machine milking induced repeatable, short-term changes in thickness of the teat apex. These changes were measured with a spring-loaded caliper instrument under milking conditions that imposed differing forces on the teat apex. The mean percentage changes in teat end thickness (relative to the premilking values for individual teats) varied from 10% decrease up to 20% or more increase depending on the particular milking system used. The overall decrease in teat end thickness associated with cannula milking, milking at very low vacuum levels or milking with positive pressure pulsation may result from: (i) decrease in the intramammary pressure; and/or (ii) small changes in tone of teat musculature; and/or (iii) changes in the distribution of interstitial fluids in the teat apex. The overall increase in teat thickness caused by conventional or PKME milking systems results mainly from oedema (the extravascular accumulation of fluid). It is likely that milking equipment can, and should, be designed to minimize circulatory impairment resulting in oedema of the teat.Small changes in thickness of the teat apex were measured reliably and repeatably with a spring-loaded caliper instrument known as a cutimeter (Hamann, 1987;). Subsequently, this instrument was modified to provide a constant load to the teat independent of the initial diam. and to measure changes in thickness of the teat apex in response to changes in the load applied. The repeatability of measurements obtained with this modified caliper instrument was excellent over the whole pressure range, the coefficient of variation being about 2 % at low (1-2 kPa), medium (5-7 kPa) or high (10 kPa or more) levels of pressure applied to the teat (Hamann et al. 1988).The paper describes four studies, in the research herd at Kiel, designed to measure the changes in teat end thickness under a range of milking conditions and to determine the cause of the changes.

Vacuum level for opening the teat sphincter and the change in the teat end wall thickness in response to the machine milking of indigenous Greek goats

“…Similar results were reported by Peris et al (2003a,b) in the Manchega sheep breed (-0.38 mm) in a working vacuum of 36 kPa. In cows Hamann and Mein (1990) found an increase in TEWT after milking that was 2% at 30 kPa, 8% at 50 kPa and 21% at 70 kPa. Later, Hamann et al (1993) also found that the teats of cows were significantly thicker in higher vacuum levels.…”

“…For all dams, every 2 weeks during both the morning and the afternoon milking the teat end wall thickness (TEWT) was measured with a cutimeter before and after milking (Hamann and Mein, 1990;Marnet et al, 1999). Differences in the thickness before and after the milking were calculated, and the percentage change in post-milking TEWT was calculated as proposed by Hamann et al (1996b).…”

“…Researchers have found a significant relationship between milk emission kinetics parameters and the teat characteristics in goats and cows. In cows, an increase in the teat end wall thickness (TEWT) was observed after milking (Hamann and Mein, 1990). Gleeson et al (2004) found in cows that vacuum levels of 50 and 40 kPa gave similar changes in the teat tissue after machine milking.…”

Dynamics of teat-end vacuum during machine milking: types, causes and impacts on teat condition and udder health – a literature review

“…The pressure should be high enough to allow the massage effect on the teat end when the liner is closed. Blood and lymph vessels and the extracellular spaces in the teat tissue are dilated as the intra-and extravascular fluid accumulates in the teat tissue during milking (Hamann & Mein 1990;Zecconi et al 1992;Koning & Ipema 2000;Neijenhuis et al 2001). If the massage effect of the liner is insufficient, the fluid stays in the teat tissue, and changes of the pliability of the teat tissue cause a decrease in the resistance of the teat canal to bacterial invasion (O'Shea 1987;Neijenhuis 2004).…”

“…Congestion, increased teat-end callosity, hyperkeratosis, teat orifice erosion or cyanotic teat ends seem to lead to an increased risk of udder infection. Damaged tissue regions provide good physical conditions (Langlois et al 1981;Natzke et al 1982;Bulletin of the International Dairy Federation 215 1987;Hamann & Mein 1990;Zecconi et al 1992;Neijenhuis 2004) and allow direct adherence of pathogens to colonize the teats and to invade the udder (Neave et al 1969;Bramley et al 1979;Myllys et al 1994).…”