Part 1
In order to reduce mastitis and maintain milk quality, producers need to maintain milking equipment in good working condition. Adequate effective reserve, consistent pulsation, replacement of liners, and proper system vacuum levels are important factors that lead to effective milking of cows. However, milking efficiency should be considered from two other perspectives, the amount of time the milking cluster is attached to the udder (unit on time) and the percent of unit on time that milk is flowing at or near maximum. When milk isn’t flowing while the unit is attached, it is not only inefficient, but more importantly, damages the teat tissue, which may increase the risk of mastitis and decrease milk yield.
A large majority of dairy farms have their milking equipment evaluated and maintained on a routine basis. Although proper equipment function is necessary for milking efficiency, it does not necessarily guarantee it. Two management areas that could lead to poor milking efficiency are milking routines that don’t achieve consistent milk letdown and overmilking. Either one of these problems can leave cows ‘high and dry’ for a period of time, and expose teats to high vacuum levels. In this article, we’ll discuss the first of these issues, poor milk let down or what is commonly called bi-modal milking.
During stimulation of teats before milking, nerves carry an “electric signal” to the brain. On receiving the signal, the brain then releases oxytocin into the blood and then to the udder. It takes about 1 to 2 minutes for oxytocin levels to increase in blood to optimally contract muscle cells that surround the milk ducts, which then squeeze the milk down towards the teats. The two important points about this oxytocin release are enough stimulation (at least 10 seconds of actual physical touching) of the teats and the duration of the ‘lag time’, that is, the time interval between when teats are first stimulated until the cluster is attached. Unfortunately, with increasing herd size, the number of cows that can be milked through the parlor per hour, or parlor turnover rate, is often identified as one of the choke points of herd capacity. Thus, parlor efficiency is emphasized at the expense of milking efficiency.
How would you know if this is happening in your herd? One method is to measure milk flow with digital vacuum recorders (VaDia®, Biocontrol NA). VaDia units record vacuum in the mouthpiece chamber (at the opening of the liner) and in the cluster. VaDia units don’t measure milk flow directly, but give us a qualitative snapshot on milk flow. A simple way to interpret VaDia results relative to milk flow is:
High Milk Flow = Low vacuum in the liner or cluster
Low Milk Flow = High vacuum in the liner or cluster.
VaDia units can measure vacuum levels at four different places on the cluster simultaneously. We often measure vacuum in the mouthpiece of a front and rear liner, near the cluster and in a short pulsation tube.
In the example below, Cow 1 was ready to milk; the vacuum in the liner mouthpiece near the teat (red and blue lines) dropped quickly (less than 10 seconds after the unit was attached) and remained low until each teat was finished milking (the front quarter [blue line], finished before the rear quarter [red line]).
What about Cow 2? Vacuum in the liner mouthpiece and cluster (green line) decreased, but then increased to near maximum levels, and finally decreased again. This cow was not ready to milk, milk flow was low for more than a minute after the milking unit was attached, signifying bimodal milk letdown.
So how does bimodal milking relate to milking efficiency? For cow 1, milk was flowing for about 4 minutes and 30 seconds of the total unit on time of 4 minutes and 45 seconds. Thus, the efficiency of this milking was 95%. For cow 2, milk was flowing for about 2 minutes of the total 3 minutes and 15 seconds the unit was attached, or a milking efficiency of about 60%. Why does this matter?
Recent research from Wisconsin found that when teats are subjected to high vacuum (as in the case for cow 2) blood is congested within the teat, the diameter of the teat canal decreases, which then decreases milk flow (Penry et al., 2018). This can be detrimental to the heath of the teat tissue and possibly impair both immune defenses of the teat as well as milk yield. In the case of cow 2, in order for all of her milk to be harvested during the milking, she would have had to compensate with a higher milk flow rate in a shorter duration of time, despite the anatomical changes to her teat during high vacuum, which is unlikely.
A proper premilking routine should result in at least 90% of cows with immediate milk let down after cluster attachment, and milk should be flowing 95% of the time while the cluster is attached. In a subsequent article, we will discuss the other problem that leads to poor milking efficiency, overmilking. For more information on the use of VaDia recorders to describe milk flow visit the Quality Milk Alliance article site: Let the Cows Score the Milking Protocols
Part 2
In Part 1 of this series, we discussed milking efficiency, defined as the percent of unit on-time (cluster attached) that milk is flowing near maximum. For example, if a milking unit is attached for 5 minutes to a cow during milking, and strong milk flow occurs for 4 minutes and 45 seconds, her milking efficiency is 95% (285/300 seconds). When milk isn’t flowing while the unit is attached, it is not only inefficient, but more importantly, can damage teat tissue, and thus may increase the risk of mastitis and decrease milk yield.
As stated in the Part 1, most dairy farms evaluate and maintain their milking equipment on a routine basis. Although proper equipment function is necessary for milking efficiency, it does not necessarily guarantee it. Two management areas that lead to poor milking efficiency are milking routines that don’t achieve consistent milk letdown and overmilking. Either one of these problems can leave cows ‘high and dry’ for a period of time, and expose teats to high vacuum levels. In this article, we’ll discuss overmilking, which is an problem that occurs at the end of milking.
After a milking is completed, the vacuum should be turned off and cluster removed from the cow as soon as possible. Removal of the units is usually done by automatic detachers (take-offs) that rely on sensors that record milk flow between the cluster and milk pipeline. When milk flow remains at a low level (about 0.5 lbs/minute) for a few seconds, the vacuum shuts off and the cluster is detached from the cow. However, if herds lack detachers, or if operators intervene in deciding when a cow is done milking, units may be removed manually. Generally, it is undesirable to have units attached for more than 15 seconds after milking completion and units that are attached for more than 30 seconds after milking are considered to be overmilking.
How do you recognize overmilking? A simple way is to hand strip the udder after the unit is detached. A cup of milk should be easily attained without overworking the teats. As mentioned in Part 1, milk flow can also be estimated with digital vacuum recorders (VaDia®, Biocontrol NA). A simple rule for interpreting VaDia results relative to milk flow is:
High Milk Flow = Low vacuum in the liner or cluster
Low Milk Flow = High vacuum in the liner or cluster.
VaDia units can measure vacuum levels at four different places on the cluster simultaneously. We often measure vacuum in the mouthpiece of a front and rear liner, near the cluster and in a short pulsation tube.
In the example below, Cow 1 was ready to milk; the vacuum in the liner mouthpiece near the teat (red and blue lines) dropped quickly (less than 10 seconds after the unit was attached) and remained low until each teat was finished milking (the front quarter [blue line], finished before the rear quarter [red line]). At the end of milking, although the front quarter was done milking for nearly two minutes before unit take-off, the rear quarter continued to milk until about 15 seconds before unit take-off and thus was not overmilked. Cluster vacuum (green line) continued to fluctuate in a range of about 2 inches of mercury (inHg) during this time, suggesting milk flow for the cow was continuous.
What about Cow 2? Milk flow started soon after cluster attachment, but vacuum in both the front and rear quarters increased to near maximum and plateaued 2 minutes before unit take-off. Also, the cluster vacuum (green line) increased to maximum vacuum during this time with little variation, which suggests little or no milk flow. This cow was overmilked.
So how does overmilking milking effect milking efficiency? For cow 1, milk was flowing for about 4 minutes and 30 seconds of the total unit on time of 4 minutes and 45 seconds, or a milking efficiency of about 95%. For cow 2, milk was flowing for about 4 minutes and 30 seconds of the total milking time of 7 minutes and 30 seconds, or a milking efficiency of about 60%. Why does this matter?
Unnecessary high vacuum is never good for teat health. Additionally, it is very common for overmilked cows to have extended unit on-times. This reduces cow throughput in the parlor and also extends the length of time that is needed to milk a herd. Also, slower parlor efficiency requires cows to stand in the holding pen and parlor for longer periods of time, reducing the time they spend resting and eating. Anecdotally, by reducing overmilking and decreasing unit on time by just a couple of minutes per cow, some herds have reported decreasing the duration of a milking shift by at least 45 minutes, or decreasing the total milking time by about two hours per day for a three time a day milking herd.
The most common causes of overmilking are lack of automatic detachers, automatic detachers that are not operating properly, or the tendency to have milking operators place the detach mode to manual. This often occurs when operators are frustrated with detachers that aren’t functioning well, or the mistaken belief that cows need to be milked out dry. Cow 3 (below) is a VaDia plot of overmilking that occurred from re-attaching the cluster after the cow was done milking, note the drop in all vacuum lines while the unit was off the cow.
Herds that have shorter duration of milking shifts are more likely to have increased overmilking as opposed to herds that are using their facilities for the maximum hours each day. For more information on VaDia analysis, or to read the previous articles in this series, please go to the following links: Let The Cows Score The Milking Protocols
Part 3
n Parts 1 and 2 of this series, we defined milking efficiency as the percent of unit on-time (cluster attached) that milk is flowing near maximum. For example, if a milking unit is attached to a cow for 5 minutes during milking, and strong milk flow occurs for 4 minutes and 45 seconds, her milking efficiency is 95% (285/300 seconds). When milk isn’t flowing while the unit is attached, it is not only inefficient, but more importantly, it can lead to high vacuum on the teat, which damages teat tissue, and thus increases the risk of mastitis and decreases milk yield.
Also in the previous articles, we described the two major management problems that lead to poor milking efficiency ̶ milking routines that resulted in delayed milk letdown (bimodal milk letdown) and overmilking. Either one of these problems can leave cows ‘high and dry’ for a period of time, and expose teats to high vacuum levels. In this article, we’ll discuss herd goals for milking efficiency to help increase awareness of this concept for dairy producers and managers.
It is nearly impossible for a cow to be in full milk flow for 100 % of the time that the cluster is attached. Often, there is a slight delay in milk flow after unit attachment. Depending on the settings for terminal flow and delay of the automatic cluster removers (automatic take-offs), the units will remain attached for brief periods of low milk flow at the end of milking. Also, milk let down will vary between cows in a herd, despite consistent milking protocols. Thus, fresh cows, nervous heifers, or cows in estrus, may deviate from the herd average. Nonetheless, if sound milking preparation is combined with timely cluster removal, the vast majority of cows will be exposed to only brief periods of high mouth piece chamber vacuum (the vacuum that “surrounds” the teat) during milking.
The figure below displays the milking efficiency for 57 herds milking from 65 to over 3,000 cows in a variety of milking systems, although no robotic milking systems were evaluated. The average milking efficiency across all herds was about 78%, that is, cows in a typical herd are in high milk flow for only 78% of the time that the cluster is attached. The bottom 25% of herds had a milking efficiency of 72% or less, the top 25% of herds 86% or better. Top herds (top 10%) had a milking efficiency of nearly 90% or better. Thus, these top herds serve as indicators of what to expect when timely and consistent milk letdown and cluster removal at the end of milking are practiced.
Milking efficiency is more than a score for your herd. More importantly, it can help draw attention to possible opportunities to improve teat health, mastitis control and milk production. As pointed out in earlier articles, the exposure of cows to bimodal milk let down and overmilking varies between herds. If milking efficiency is low (<80%), this suggests that milking practices, both before and at the end of milking, as well as equipment function, should be reviewed and evaluated. You don’t need VaDia recorders or other milking analysis equipment to get a ‘thumbnail sketch’ of possible problems in milking dynamics. For example, you can simply watch milk flow into the cluster after attachment, or look at teats for rings or congestion (discoloration) after the units come off. This is not unlike checking for the completeness of covering teats with a germicide after milking.
Top herds achieve the ideal goal of machine milking ̶ the cluster is attached only while while milk is flowing, which optimizes teat and udder health and milk harvest. What are your milking goals?
Source:qualitymilkalliance.com
