The function of a liner
During the milking process, the liner opens and closes to interrupt the milk flow due to the pressure difference between the inside and outside of the liner (pulsation). Closure of the liner wall exerts pressure on the teat, which can be seen as massage. The massage ensures the back flow of fluids such as blood and lymph, but can also be a burden on the teat and cause hyperkeratosis on the teat end.
The default Lely liner suits most cows. However, within a herd it is always a compromise as teat size can vary widely. This is even more the case with multiple breeds in a herd, a breed with a small teat diameter or a robot group with only heifers. The most important specifications are explained below:
Mouthpiece diameter : 21 mm suits average/normal teats.
Rings versus flat head: rings on the head of the liner, see figure 2, give more resistance against tearing.
Short head versus high head: high and small heads suit narrow teat positions, while short heads have a higher pulsation room for better massaging on short teats.
Small Ø head versus normal Ø head: choice depending on teat size (length and diameter).
Finding the right liner
Before looking at the liners and variations it is recommended to keep, among other things, the following in mind:
- Joined forces between technical services and Farm Management Support.
- Check up front (technical) settings such as the milk access table, MT, DMT, time in between brushing and connection, cleaning performance, pulsation test, cleaning temperature, vacuum, pulsation, etc.
- Remind that the standard liners are suitable for most farms.
For good insights into the milking process and the fitness of the liner, several actions can be performed:
- Teat end scoring, measuring teat length/thickness. Score at least twenty cows per robot on all quarters, using a representative mix of cows (early, mid and late lactation).
- Take pictures to be able to compare in a few months.
- Use a dedicated tool to measure this before milking and without any stimulation.
- A dynamic measurement test checks the milk vacuum at the teat end and mouthpiece vacuum during milking.
Choosing the correct liner is a matter of learning by careful trying and strict monitoring. An insufficient liner can cause visual signs, such as liner slips, small hemorrhages on the teat end, teat end congestion or even blue teats.
Choosing a liner (and appropriate milk settings) is an exercise in balancing the goals of milking quickly and gently. Too little liner compression can result in teat end congestion, while too much liner compression can result in teat end hyperkeratosis. For a well-considered choice, get in contact with your Farm Management advisor from the Lely Center.
Lely Farm Management Support