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OSU Extension

College of Food, Agricultural, and Environmental Sciences

November 27, 2018 - 8:01am --

             When I was growing up on a dairy farm, I was taught to milk cows as completely as possible every milking.  An article about overmilking from the Penn State Extension dairy web page ( says that taking that approach with today’s high yielding dairy cows is a no-no because it is nearly impossible to milk a cow completely dry.  A healthy lactating cow makes milk continuously.  Routine overmilking causes roughened teat ends, leads to higher somatic cell counts, increased risk of infections, and decreased udder health.  Here is a summary of that Penn State article:

            Physiologically, overmilking begins to occur when the milk flow to the teat cistern is less than the flow out of the teat canal.  This creates a situation where the vacuum in the teat cistern is higher than the vacuum at the teat end resulting in a reverse pressure gradient.  This reverse pressure gradient provides an opportunity for bacteria to move from the teat end up into the teat cistern.  Long milking unit on times often result in hyperkeratosis of the teat ends.  Hyperkeratosis means excessive keratin growth.  Visually, the end of the teat has rough spots and/or wart-like structures.  Teat ends in this type of condition are difficult to thoroughly clean, increasing the risk that bacteria left behind will find a way into the teat canal.  As a result, these cows are more likely to have higher somatic cell counts.

            According to that Penn State article, periodically performing a strip yield test can tell you if you are overmilking.  The strip yield test is an evaluation of milking completeness.  To perform the test, immediately after milking hand strip each quarter for fifteen seconds into a measuring cup.  If your milking procedure is correct, you should end up with about one cup of milk in the container.  Significantly, more milk in the container indicates a need for more complete milking.

If the strip yield test yields less than a cup, make adjustments in the milking routine.  If automatic milking unit detachers are used, then adjust the flow setting that triggers removal.  If milking units are manually detached, then milkers need to become aware of the issue and need to adjust their routines to match the end of milking with individual animals.

Using a strip yield test to help prevent overmilking is not a costly management practice, but it can result in economical returns with better teat end condition and better udder health.


Rory Lewandowski is an OSU Extension Agriculture & Natural Resources Educator and may be reached at 330-264-8722.

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