Recently, I was returning home from two farm visits at which I discovered that both farms had been dutifully replacing their rubber teat cup liners every twelve months, just as they had done for many years.
While I was contemplating liner change intervals in the car, I passed a car on the side of the road accompanied by a police car with lights flashing.
Because the traffic was slow, I observed the driver and the policeman having what appeared to be an animated discussion whilst pointing to what were obviously very bald tyres on the car.
The policemen already had his “ticket book” in his hand, so I thought the driver was unlikely to win that one, and would probably receive both a financial penalty and some licence demerit points.
It then occurred to me how lucky we are with car tyres that we can actually see when they are worn out, and there are also wear indicators built into the rubber tread!
However, with rubber teat cup liners there is commonly no visible sign of deterioration as they age – yet just like car tyres, they begin to wear from the time they are first installed!
If milking machines operate for 4 hours per day, then with a pulsation rate of 60 cycles per minute, the liners will open and close 14,400 times in a day, or 432,000 times in a month.
The rubber will actually begin to absorb some fat from the time the liners are installed, and if there is a wash cycle twice a day, they will undergo a chemical wash 60 times in a month.
So it is little wonder that liners wear out!
After 12 months of this intense work on the farms I visited, the liners would have opened and closed 5 million times, and been subjected to 730 chemical washes - they would probably be close to “dead”!!
Now consider that when operating, the liners are actively closed by vacuum in each pulsation cycle, but they actually open again entirely due to the tension & resilience of the rubber – there is no other force, vacuum or otherwise, involved.
As they wear out, they progressively lose tension and resilience, so they can no longer apply the same forces and massage the teats as they did when new, resulting in a degradation of milking performance and a far higher risk of teat end damage.
Consequently the risk of mastitis is greatly increased!
When badly worn, you may notice a bit more cup slip or poorer milking; if you do notice these changes, or if you notice any change after you change your liners, then the old ones were definitely in for too long!
How often should liners be changed?
The Countdown 2020 Farm Guidelines for Mastitis Control and milking equipment manufacturers recommend changing liners after 2500 cow milkings or 6 months, whichever occurs first.
The Countdown Mastitis Toolkit app (available free for both iOS and Android smartphones) has a liner life calculator which calculates the 2500 cow milkings when liners are due to be changed and allows you to set a reminder alarm for that date.
For most farms, this will be the right timetable; however, just as car tyres don’t do the same number of kilometres on every car with every driver, there are other factors that may cause early deterioration in rubber teatcup liners.
Exposure to sun, heat, chemicals & ozone all contribute to deterioration in liners, but perhaps the most common and most destructive influence that we see is the use of chemical (usually alkali) “bombs” for plant cleaning.
These “bombs” have a huge effect on rubberware and can probably be compared to the effect of a car doing “burn outs” on its tyres – neither will have a long life afterwards!!
The unfortunate driver with the policeman was receiving a penalty for driving a vehicle that was at a greater risk of having an accident. If you have worn out liners in your dairy, you have a greater risk of having a mastitis “accident”, and suffering the resulting financial cost.
Perhaps it is time for a change!