Every cow has four milking machine testing units; they are her teats. The milking machine liner is the only part of the machine in contact with the cow with that contact occurring at the teat end and along the teat barrel. It is a unique “marriage” between a biological system and a machine that is very important despite it only occurring for between 10 and 15 minutes per day. We all know that teats in an individual herd differ in length and width yet all teats have to change shape during milking to conform to the installed liner shape. The teat changes to fit the liner and not the other way around. 
 
There is a myriad of liner choices on the New Zealand market and they differ according to liner shape, dimensions and material. While the general aims of milking are speed and gentleness, this is a balancing act, and different liners achieve this mix to various degrees. Liner performance is also affected by working vacuum and pulsation settings beyond their design. 
 
Assessing your herds teats immediately after cups off, but just prior to teat disinfection, provides an accurate picture of teat health and in, the success of the liner-teat marriage. Teats “always tell the truth”, if they are experiencing physical forces that stress teat tissue there will be visible changes that can be seen and measured across a herd. The sorts of changes that can be seen are, for example, teat end hyperkeratosis and congestion in either the teat end or teat barrel. Teat end hyperkeratosis that is increased beyond accepted trigger levels will result in elevated new mastitis infection risk. This is due to the teat end being a better place for mastitis causing bacteria to harbour compared to a smooth teat end. The same can be said for congested teats at the end of milking (red, blue or “garter marked” teat barrels). These changes can increase new mastitis risk as well as decreasing milking speed. 
 
A milking time assessment can quantify teat health in your herd and indicate if actions are recommended to the milking plant or milking process to enhance the health status. Recall that teat health, and the integrity of the teat end, is the first and major line of defence against new mastitis infections.