The liner is the only component of the milking machine that comes into direct contact with the cow’s teat. Therefore, it is one of the key components in the process of milking cows quickly, gently and completely.

Although many people try to squeeze a few more weeks or months from the liners in a dairy, this is almost always a poor option for the most important component of the milking machine.

As liners age, their shape, tension and surface condition changes gradually. This gradual deterioration can have subtle but significant effects on their milking characteristics. Both the internal surface and the milking performance of liners tend to deteriorate more quickly soon after they reach their designated use-by date.

As liners age and stretch, several key features of their milking performance alters. In particular –

• the average milking time per cow increases

• the frequency of liner slips increases

• the amount of milk left in the quarters of an udder when cups are removed increases

• the teat-end condition of the cows decreases

• cow behaviour worsens

Whilst each of these features is associated with an increased risk of mastitis, any effect on teat end condition or any increased liner slips are particularly significant risks.

As a general rule of thumb, if you notice an improvement in milking performance after replacing liners, the old ones were used for too long!

The age of liners is calculated in terms of “cow-milkings” and the Countdown Downunder Farm Guidelines show how to calculate liner life in “cow-milkings”.

Most Australian rubber-based liners can be used for 2,500 cow-milkings or 4-6 months – whichever comes sooner.

When renewing liners, always change all four liners within a cluster at the same time to maintain similar mounting tension and milking characteristics between the four teatcups.

Prevention is better than cure – change liners according to their use-by date to avoid the risks from using worn out liners.

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"As liners age, their shape, tension and surface condition changes gradually."

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