Pressure distribution at the teat–liner and teat–calf interfaces

Abstract

During milking, the teat is loaded because of a combination of vacuum and pressure of the collapsing liner. It is assumed that pressure concentrations tend to cause teat-end injuries and hyperkeratosis. The pressure distribution on the bovine teat was measured to test the hypothesis that the pressures of the collapsed liner are unevenly distributed over the teat. With the aid of a pressure-sensitive sensor (approximately 2 gauge points/cm(2)), the pressures at the teat-liner and the teat-calf interfaces were measured at 100 Hz. Pressure distribution over the surface of an artificial teat was measured with 7 different liners, 1 liner at 3 different vacuum levels, and a suckling calf. One cow was equipped with a sensor at a teat during a milking with one of the liners. Conventional round liners concentrated the load over 2 sites at the teat end. Some liners (softer material, reduced tension, smaller barrel, reduced mouthpiece depth) distributed the compressive load over a larger area of the teat. Although all liners distributed the highest pressures at the teat end, some liner designs showed a 25% reduction at the site of interest at vacuum of 44 kPa. The calf forced milk flow by a combination of suckling and overpressure in the teat cistern caused by the tongue. While the calf was swallowing, teat pressure was reduced because of a decrease in vacuum. Moreover, the calf did not load the teat end, probably because the teat canal would be closed and the milk would not flow. The method of using a pressure sensor to analyze teat loading at the teat-liner and the teat-calf interfaces showed potential and is a first step toward developing a natural milking technique.

The Usability of a Pressure-Indicating Film to Measure the Teat Load Caused by a Collapsing Liner

“…These results agree with those of Tol, Schrader and Aernouts [15]. They had found that the maximum pressure was always exerted on the teat end.…”

“…Davis, Reinemann and Mein [14] detected pressures of 20–41 kPa between the liner and teat. The artificial teats used in the present investigation could explain why the pressure values measured in this investigation are higher: in the other investigations the artificial teats were hollow and made of silicone [15]; our artificial teats were not hollow. However, the silicone teat used in the present investigation was very stiff.…”

“…These pressure values are much higher than those found in other investigations. The pressure measured by Tol, Schrader and Aernouts [15] was 99–180 kPa at the teat end. Muthukumarappan et al [20] measured a pressure of 18–35 kPa between a teat and a collapsing liner.…”

“…The sensor was covered using natural gum rubber and a gel-like material. Tol et al [15] investigated the teat-liner interface with the help of a flexible pressure-sensitive layer. The layer included carbon particles and was attached to a resin film through which electrodes faced each other.…”

The Use of a Pressure-Indicating Film to Determine the Effect of Liner Type on the Measured Teat Load Caused by a Collapsing Liner

“…Davis et al [13] measured the compressive load applied to the teat by the closed liner using an artificial teat equipped with a miniature load cell and found that the compressive load of a liner is proportional to the thickness of the liner wall; the authors determined a curvilinear relationship between the insertion depth and the compressive teat load as well. Tol et al [14] investigated the teat-liner interface using a flexible pressure-sensitive layer and found that conventional round liners concentrated the load over two sides of the end of the teat. In contrast, liners with softer material, reduced tension, a smaller barrel, and reduced mouthpiece depth distributed the pressure over a larger area of the teat, but the maximum pressure was always exerted at the teat end.…”