Extending dairy liner life a false economy

Using dairy liners beyond their recommended lifespan could be costing producers up to £15 per day in lost milk production and increased vet costs. According to Milk-Rite's Derek Davies, the recommended frequency of change is often overlooked by producers, with some extending their use to over twice the recommended lifespan.

The changes that take place in liners over time alter their physical properties, particularly their size, shape and elasticity. Where liners are not changed as recommended, teat health can be adversely affected, ultimately resulting in permanent damage and an increased incidence of mastitis.

Milk Rite's material development centre, in association with the Institute of Animal Health in Compton, has undertaken extensive assessment of the factors that affect liner life. The work has shown that rubber absorbs small quantities of water and butterfat causing swelling and "creep". Creep causes a relaxation of the tension in the barrel of the liner, resulting in inadequate teat massage. This can lead to redness, bruising and even bleeding.

The internal surface of the liner often becomes rough as a result of a black calcium and phosphorus deposit, known as "milkstone". This is not, as many people believe anything to do with the degradation of the rubber. The rough milkstone layer increases the friction between the liner and the teat and also causes local hardening of the rubber that comes into contact with the teat. This increased friction is thought to put more stress on the teats.

"While there are measures that can be taken to reduce the rate of liner change, these are often impractical. The only way to ensure that liners are not responsible for any adverse effects on teats is to change them after every 2,500 milkings," advises Mr Davies.

For 200-cow herd, milking twice a day in a 12-unit parlour, 2,500 milkings equates to a change interval of 75 days. Table 1 gives an indication of the typical costs of extending the frequency of change to up to twice the recommended period.

"Dairy liners are the only part of the milking machine that comes into contact with the cow, so their importance cannot be over-emphasised," claims Mr Davies. "Any potential savings made by reducing the frequency of change are a false economy, as the damage caused by worn out liners can be, and often is, permanent."