The field detection of “inter-unit milk flow” in pipeline milking equipment

Abstract

Extract

There are many ways in which a milking machine can transmit infection from cow to cow. The immediate transfer of infection by the, teat-cups is obvious and the reduction of the effectiveness of this vector has been shown to reduce the incidence of mastitis (Wilkinson, 1965). The change from bucket to pipeline milkers has been associated with an increase in the incidence of mastitis arid this has been attributed to the vacuum instability of the latter system. Fell and Richards (1970) have studied the relation-ship between machine stability and the level of somatic cells in milk, and Whittlestone and Fell (1969) have suggested that milk line vacuum instability could be associated with flow conditions that could give rise to the movement of potentially infected milk from the pipeline back into the clusters. This potential vector has been overlooked in the past but its presence, would clearly negate the beneficial effects of “back flushing”. A field study was therefore undertaken to estimate the frequency of occurrence of the “inter-unit flow” effect in pipeline systems, and Whittlestone et at. (1970) found a high incidence of milk movement back to the cluster in high pipeline systems though the effect was not found amongst the limited number of low-line installations examined. Two types of “inter-unit flow” were detected: whole liquid movement which appeared as liquid milk in the measuring trap inserted between the cluster and the milk pipe, and “aerosol” which could only be detected by the use of plugs of cotton wool inserted in the test teat-cups. Evidence for the presence of “aerosol” and its role in transmitting infection within the cluster has been collected by A. Tolle (pers. comm.). This establishes the possibility that once infected milk has reached the cluster it can be transferred to the, end of the teat during milking.