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How to evaluate completeness of milking

As information can change over time, If you read this outside of 6 months from the original post date, please confirm with your WCR advisor that the information is still valid and accurate.


The milking that most benefits both the cow and the robot is a complete milking. Complete milkings provide

a solid foundation to further optimize the milking process and shorten cups-on time. A complete milking

means that all available milk is collected from the udder, without overmilking. This stimulates milk

production (Penry et al., 2017, Albaaj et al., 2018) and contributes to efficient Astronaut use



Figure 1: Circle of improving milking performance.

Figure 2: Square milk flow profile, indicating a complete milking.


Complete milkings are characterized by a square milk flow profile. This indicates a continuous milk removal from the quarter until milk flow ceases (figure 2). Taking the teat cup off too early or teat congestion are the main reasons for incomplete milkings. But how can you evaluate whether a milking was complete?


Take off on airflow & teat signals

One indication of incomplete milkings are teat cup take-offs before the milking is finished. Kicking cows or liner slip can result in too early take-off near the end of milking. In these cases, the milking is not finished because of milk flow, but because of the presence of air flow. When the Astronaut recognizes too much air flow it will take off the teat cup, if this happens after 80% of the expected milk time, the teat cup is not reconnected. In LSSA (figure 3), this can be seen as take-off reason on airflow. On average, take-off on airflow is below 3.7% for all Astronauts worldwide, while the top 10% of the farms reached less than 1%.


An important parameter for complete milkings, but less often thought of, is the absence of congested teats. Congestion of the teat can result in milk “trapped” in the udder. When congestion builds up during milking, the teat canal gets blocked, preventing milk flow from the udder cistern to the teat (figure 4). Wrong liner fit, too high vacuum or the occurrence of bimodality can result in build up of congestion. A slow decline in milk flow rate during the milking indicates potential build up of congestion. Visual inspection of teat signals directly at the end of milking can show whether congestion is present (see figure 5).


Figure 3: Take off reasons that FMS support can see

Figure 4: swelling obstructing the teat canal at the teat base (L) or teat end (R)
Figure 5: Swelling of teat base directly after milking

Should I check strip yields?

Manual strip yield milking is a common way to evaluate completeness of milking. In most literature it is referred to as a maximum of 250 - 500 ml for the whole udder, and 40 - 100 ml per quarter with 15 seconds of hand milking. If the milking was complete, you should not have more than 4 - 5 strong sprays of milk per teat (Meyer et al., 2020). The strip yield milking needs to be done as soon as possible after the milking, because otherwise congestion might be partially relieved. Be aware of your own safety while doing the strip yield test and do not perform a strip yield check in the Astronaut.


Whether to check strip yields or not depends on the situation. The presence of congested teats or take-off on airflow indicates already that the milkings are likely incomplete. Manual strip milking on congested teats can also lead to wrong conclusions, since the congestion results in a (partially) blocked teat canal, preventing milk flow also with hand milking. Therefore, it is recommended to solve take-offs on airflow first or prevent the cause of congestion.


What could a dynamic test tell me?

A dynamic test provides insight into vacuum levels and pulsation during the milking process. A complete milking can be seen on a dynamic test result as a square profile and stable vacuum levels for teat end vacuum and mouthpiece chamber vacuum. Ideally, teat end vacuum should stay blow 39 kPa (11.5 inHg) and mouthpiece chamber vacuum in the range of 5 to 20 kPa (1.5 to 6 inHG). For mouthpiece chamber vacuum, a lower number in the lower range and cyclical movement is better. In case of congestion of the teat, milk flow rate declines resulting in a gradual increase in mouthpiece chamber vacuum or teat end vacuum.


Figure 6: Perfect dynamic test outcome. Stable and high milk flow rate as indicated by the teat end vacuum (green line) and minimal rise in mouthpiece chamber vacuum (red line) and for a short duration towards the end of milking when milk flow has ceased. In this case, mouthpiece chamber vacuum is the inverse of milk flow rate.

Figure 7: Dynamic test outcome showing bimodality at the start of milking and an increase in mouthpiece chamber vacuum levels (red line) during the entire milking. Congestion build up is more severe when the bandwidth of the mouthpiece chamber vacuum (red line) is smaller or just a line. Milk flow drops after the bimodal event as seen in the smaller band width of the teat end vacuum (green line) and remains low afterwards. Combined with the high mouthpiece vacuum this indicates congestion, resulting in a vicious cycle of further limiting milk flow and build-up of congestion. In this case, mouthpiece chamber vacuum is the inverse of milk flow rate.

Figure 8: Dynamic test outcome showing take-off on airflow mid milking followed by a re-attach and two times liner slip. These events are shown by a rapid and immediate decline in teat end vacuum (green line) and mouthpiece chamber vacuum (red line) without the decrease in bandwidth of teat end vacuum which would indicate lower milk flow or increase in mouthpiece chamber vacuum which would indicate an empty teat.

Should I extend or delay take-off settings? 

A good start is half job done. This certainly applies to achieving a complete milking. Having a good start of the milking and stable milk flow during the milking prevents congestion and contributes to complete milking.


When the milk flow is released in a “square” shaped milk flow profile, the influence of take-off settings becomes less. On



the other hand, the influence of take-off settings on take-off moment for congested teats with a slow end is bigger (see figure 9). Therefore, solving the reason for congestion will improve milking performance for these cows. This can be done by adjusting milk access and pretreatment times to prevent bimodality, or liner fit, vacuum and pulsation to prevent congestion.


Delaying the teat cup take-off moment does not solve the reason for incomplete milking, being either too early take-offs by airflow or congestion of the teat. In case of congestion, extending the take-off moment can result in overmilking and thus resulting in more congestion and potentially teat end damage in de long term.




Figure 9: Effect of two different take-off levels on take-off moment for a complete milking (L) and milking with a slow end (R). The effect of the take-off level has a smaller effect on actual take-off moment for the square shaped milking compared to the slow ending milking.

What do cows that are leaking milk tell me?

Leaking milk can be seen at different moments, e.g. leaking milk shortly after milking, in the cubicles or before milking. When leaking milk happens after milking is finished, it can be due to relieved congestion after milking. This can be a signal that the milking was incomplete. Check teats for congestion can provide further insights.


Take home message

  • Good milking performance makes determining the end of the milking easier, resulting in a complete milking without “overmilking”. By preventing too early teat cup take-offs by airflow or by preventing teat congestion, all milk is collected from the udder.

  • When in doubt whether the milking was complete, evaluate take-off reasons or teat signals after milking. Take off on airflow should be limited and the teat should show no signs of discoloration or swelling (see figure 10).

  • Delaying the take-off moment to complete the milking puts more stress on the teats without actually achieving a complete milking. Due to the congested teat, milk will be left in the udder. Fix the reason for congestion and thereby improve overall milking performance, instead of trying to fix the issue at the end of the milking, when harm is already done to the teat.


Figure 10: Teats after milking with optimal milking performance: Slightly wrinkled, soft skin, even color & dry teat No swelling, no red or blue discolorations ‘Orange peel’-like texture

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