Liners and Teat End Health

In the dairy industry world wide, several hundred types of liners are used to milk dairy cows. The enormous amount of liner types with different characteristics in size, form, consistency and other design and manufacturing characteristics indicate that no ‘best’ liner has been identified in the last 60 or so years since machine milking has become the common method for milk harvesting. Mechanical liner characteristics have been studied using mathematical force models and observed collapse usually under laboratory conditions (Butler 1993, Harty et al. 2004). Recent work by Teat Club International (TCI) has mapped explanations and descriptions of teat and liner interaction. The most descriptive explanation of this complex phenomenon has been defined as “overpressure” or “compressive load” as that relates to the action of the liner, the efficiency of milking and the maintenance of teat and teat end condition (Mein el. al. 2003). Preferences of farmers for liner type have been influenced by balancing different aspects of milking performance, replacement rate and price per milking. Liner performance may be assessed by milking performance (milking speed and milk out), incidence of intra-mammary infections (IMI), cow behavior and teat responses (Hillerton 2005). Although many criteria are used for selection of a liner, performance of a particular liner ultimately rests on the ability of the liner to efficiently remove fluid milk during the milk harvesting process and simultaneously maintain teat end condition. However, formal guidelines for evaluating liner performance do not exist. There are no guidelines that are, for example, comparable to the NMC teat disinfection evaluation protocol. This makes objective evaluation or recommendation of liners difficult if not impossible.