Dairy cow milking: teat cup liners

The milking machine is the most important piece of equipment on a dairy farm, and as part of its maintenance, it’s vital to change teat cup liners regularly. Liners are the only part of the milking plant that come into contact with the cow, and their condition is critical in mastitis control and for efficient milking. 

A liner must be designed specifically to fit the teat cup shell for which it’s intended and, more importantly, for the cows’ teats. To avoid teat congestion, liners should be long enough to collapse fully around the teat base and allow proper blood circulation. 

When the interior of the liner becomes rough, it can be more difficult to disinfect and can act as a reservoir of infection, leading to an increased risk of cross-contamination between cows. It can also increase Bactoscan readings. 

Liner lifespan 

Liners have a limited effective life – generally around 2,000 to 2,500 milkings for rubber-based liners and 8,000 for silicone liners. However, many factors can affect liner lifespan, and it’s essential to check their condition frequently, as defective liners occasionally fail early in their quoted lifespan.  

Liners are damaged by normal wear and tear and by chlorine and other chemicals used in the milking plant, which weakens the rubber-based liners in particular. This leads to loss of elasticity, roughness, perishing and splitting. If you regularly backflush your liners with peracetic acid, you may need to change them more frequently. 

Most liners come with information that enables you to calculate their expected lifespan. Use the simple calculations in the table below to check how often you need to change liners.

Note: The cells with bold text indicate an example of farm data 

When cluster units aren’t disinfected, the infected milk residues left behind can cross-contaminate the following six to eight cows to be milked with that cluster. That’s why it’s vital to use an appropriate disinfectant to wash clusters after milking a cow with clinical mastitis or a high SCC, whether a separate cluster is used or not.  

If you’re not using a dump bucket, the plant back to the recording jar/meter should also be back-flushed with a disinfectant where possible. 

If you can’t segregate infected cows and milk them last in the milking order, you may be able to reduce transmission risk by disinfecting the cluster and milking equipment between cows, either manually or via an automated system. 

Automated liner/cluster disinfection 

Automated back-flushing systems are increasingly popular. These may help to save time in the parlour and improve cow flow while maintaining udder health. However, there’s currently no evidence to show a significant reduction in the rate of new infection in lactation or even a reduction in bacteria numbers on the liner. 

Manual liner/cluster disinfection 

The best way to flush the cluster unit is to dip it in a bucket of disinfectant solution. Dip two teat cups at a time, so there’s no air pressure build-up in the cluster unit, to prevent the solution from entering the liners.  

It’s important to ensure that the liners don’t touch the parlour floor. Peracetic acid disinfectants are less likely to damage parlour rubberware during this procedure. When you’re regularly exposing liners to disinfectants, you may need to change them more often if there’s evidence of damage.

Weekly checks 

Check for twisted liners 

Ensure liner markings on the hood and short milk tube are aligned. 

Check liner condition 

Liners should be changed every 2,500 milkings or every six months, whichever comes first. Silicone liners have a life expectancy closer to 8,000 cow milkings. 

Note: it’s critical that liners are in good condition, as they’re the only part of the machine that come into direct contact with the cows’ teats. When they’re worn, they lose their shape and don’t massage the teat correctly, resulting in longer milking times and reduced yields. Worn liners are also a source of bacteria, particularly thermoduric bacteria (see AHDB/NML guide to thermoduric management), as they hide in the cracks in the liner. 

Monthly checks 

Check liner slip 

During one milking, record the number of liner slips or squawks that need to be corrected by the milker. Five or fewer per 100 cows is acceptable, while 10 or more per 100 cows requires investigation.