The Strip Yield Test

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- Traditionally the recommendation to dairy producers has been to milk all cows as completely as possible at every milking, but due to recent research and field experience this recommendation has been revised.

I'm Amber Yutzy, a Penn State Extension dairy educator and I would like to talk to you about a test that can help determine when milking is complete.

It is called the strip yield test.

Ordinarily it is impossible to milk a cow completely dry because there will always be some milk in the udder even after complete milk out.

This is because she is constantly making milk.

Over milking is a matter of concern because it may affect teat end condition and udder health.

In the past, it was believed that all milk needed to be removed from the udder to maximize milk yield, however breeding for high milk yields has provided cows with a high alveolar capacity.

Due to this, cows are more efficient as milk producers.

Over milking starts when the milk flow to the teat cistern is less than the flow out of the teat canal.

Mouthpiece chamber vacuum typically increases during over milking, and fluctuations become larger.

If the vacuum in the teat cistern is higher than at the teat end for short periods of time, the reverse pressure across the teat canal may increase bacterial invasion of the teat cistern.

Reverse pressure gradients occur only during milking of empty teats, and over milking will therefore increase the possibility of bacteria entering the teat.

Teat end health also great affected by over milking.

Hyperkeritosis of the teat is often experienced in herds with long unit one times.

This happens when over milking causes excessive keratin growth and a thickening of the skin that lines the teat canal.

Producers often notice a wart like structure or rough spots at the end of the teat.

This can be a result of poor milking management, and long unit one times.

Cows that experience these effects, are often seen to have an increase in somatic cell count.

This is due to the inability for workers to thoroughly clean teat ends suffering from hyperkeritosis, which leaves bacteria behind to enter the teat canal during milking.

Fortunately, there is a very simple way to test if you're over milking, that can be done by anyone on the farm.

The strip yield test looks at overall completeness of milking and can be done two different ways, by hand or with a unit.

I prefer to do this evaluation by hand, but your preference may differ.

To accomplish this test, immediately after the unit has been removed, hand strip each quarter for 15 seconds, collecting the milk in a container.

I use a plastic measuring cup.

A properly milked cow should have about one cup of milk left in the udder.

If there is more or less, a milk out problem may exist on your farm.

Performing this test with a milking unit requires a little more precision.

A milking meter is required when using this method.

To do so, the milking unit must be attached within 30 seconds of automatic removal and downward pressure applied.

Continue applying pressure for 15 seconds before removing the unit.

Record the amount of milk that was harvested using this method.

Once again, about one cup of milk should be left in the udder.

Routinely performing a strip yield test on your farm will help to ensure your milking units are being removed in a timely manner and udder health is being maintained.

If a problem is found, adjustments should be made to reach optimum udder health.