“The liner and its action within the milking machine is the most important part of the milking process,” he says. “The massage effect created by the liner opening and closing is essential for effective milking and teat health.”
The liner is an elastomer, which means it is able to stretch and return to its original shape many times. But the elastic qualities of its rubber or silicone start to wear during the many thousands of cycles the liner is expected to perform.
The wear of liners is caused by the action it is expected to repeat, but also by exposure to milk fat and cleaning solutions.
“Exposure to milk means the material of the liner will start to absorb fat and minerals, such as calcium. And teat disinfectants, particularly those containing peracetic acid, will cause the liners to deteriorate more quickly.”
Mr Baines adds that, over time, the ability of the liner to correctly apply massage pressure to the teat reduces: “So life expectancies are around 2500 hours for rubber and 7500 for silicone. Farmers should avoid trying to achieve more,” he stresses.
Whether left unchanged for economic or operational reasons, the liner will begin to harden, stretch, and lose its elasticity. This can lead to a reduction in milking efficiency but, more worryingly, can harm the teat and adversely affect udder health.
“It is inaccurate to use the term ‘teat-end damage’,” says Mr Baines. “It is not really damage. It’s hyperkeratosis – a hardening of the skin leading to callouses forming. This affects the teat orifice and can lead to increased somatic cell counts and greater incidence of mastitis.”
David Hyslop farms in partnership with his father and brother near Lockerbie, and has seen milking times, SCCs and mastitis rates reduce since switching to a cluster with a different liner design. He has also seen peak flow increase from 3.8 litres to 4.2 litres, and average flow rate increase from 2.8 litres to 3.2 litres per cow.
“We change the cartridges every 5000 milkings – our old liners would last half that time. And it used to take us up to three hours to change the liners, now it only takes just 20 minutes,” says Mr Hyslop.
The 410 strong herd is milked through a 20:40 DeLaval swing-over parlour. “It takes us 3.5 hours to milk, plus 30 minutes to set up and wash down,” he adds.
He has been keen to stick with his parlour and has seen significant operational improvements by changing clusters. “We have worked with Mathers Dairy for several years and they suggested the Evanza as a way for us to reduce cluster/liner slippage, calm the cows and improve efficiency at milking. We are milking 410 cows in the time it used to take to milk 385, and we are seeing more milk in the tank.”
Herd average somatic cell count has also dropped to between 90,000 cells/ml and 100,000 cells/ml, from 150,000 cells/ml. This, combined with the reduction in cases of mastitis, demonstrates the new clusters have improved cow and udder health.
“We switched to using these clusters in autumn 2020 and mastitis rates have fallen from 17 cases per 100 cows to 13 – based on just five cases during the past month,” says Mr Hyslop. The cows are also more content and less fidgety during milking, resulting in easier milkings for the staff.
“Previously, clusters would frequently slip off, let in air, upset the cows and make milking more complicated than it needed to be. This new design is easier to use, and the cows are also performing better.” He is therefore keen to move the Evanza clusters to a new parlour in the future.
But Mr Baines urges caution. “Every manufacturer is different and while certain parts may physically fit a machine, there’s no guarantee the part will perform its role in the milking process perfectly.
“This is particularly important with clusters and liners, because it is vital that vacuum and pulsation characteristics are correct for the specific liner,” he explains.
Pulsation settings are often similar between different manufacturers equipment, but rarely the same. “Producers should seek advice from a Parlour Safe-trained technician, who will fully understand the settings needed if retrofitting clusters to an existing milking parlour. Vacuum levels and pulsation rates should both be checked carefully and monitored to ensure the most appropriate level of pulsation.
“The physical properties of the liner will dictate the most appropriate vacuum and pulsation settings required to provide optimum massage for the teat,” adds Mr Baines.
Staying within the tolerances of liners can improve cow health and yield. It’s false economy to seek a longer life due to the inconvenience or cost of changing liners. “New technology has made an unenviable task significantly easier, but the principle of maintenance for all parlour equipment should be upheld to safeguard cow health and maximise milk yield,” he concludes.
