Milking machine function must be maintained to ensure cluster removal is easy for the milker, and causes no cow discomfort or teat damage.
The benefits of correct cup removal include:
- Cows are milked out but not over-milked with correct timing of removal.
- Milk quality maintained.
- Increased milking efficiency.
- Reduced animal health issues through ensuring teat damage does not occur.
How to avoid over milking
As over-milking is a more common problem than incomplete milking it is better to remove the cluster too early rather than too late.
- Clusters should be removed when there is less than 100 ml of milk in any quarter – there should be a dribble of milk flow in the sight bowl.
In New Zealand herds, over-milking can be excessive in the range of 2-5 min per cow for many herds, in both herringbone and rotary dairies. It is particularly common in late lactation or dairies that have too many clusters for the number of people milking.
- Over-milking is when cups remain attached to teats after a cow’s milk flow rate has fallen below a certain end-point (traditionally 200ml/min).
Extensive international research indicates that cows giving 10L per milking (not per day) can be milked in 5 min, while cows giving 15L per milking can be milked in about 6 min. This may be about a minute longer in New Zealand where cows commonly have less preparation e.g. teat washing, before milking.
Even so, considering typical rotation times are 12 minutes for many rotary platforms (with some cows going around twice), many cows are being severely over-milked. This can be caused by clusters being attached too early or left on too late.
Manual cluster removal
It is important to take care when removing clusters to avoid rapid inrushes of air that have been shown to increase the risk of mastitis infection.
The first step is to break the vacuum.
- Kink the long milk tube or pull the vacuum cut-off valve and wait 1-2 seconds while the claw fills with air at atmospheric pressure.
- Rotate the cluster 30 - 60° to break the seal and assist with cluster removal. When the clusters are not sliding off freely, check the vacuum to the clusters is being fully cut off and the setup of the milking machine including the compatibility of the liners with the cows and the working vacuum level.
- For large volume clusters (400 ml plus) it is necessary to kink both the long milk tube and pull the vacuum cut-off valve to reduce vacuum in a timely manner.
- Once the cluster is removed the milker should be able to hang it up on a convenient hook or swing it over to another cow.
Actions to take
- Difficult cluster removal:
- Clusters that are hard to remove, or are not releasing correctly, are a sign that the equipment is not working properly. Check the machinery if this is happening.
- Check air admission holes and repair faulty vacuum shut-off valves as soon as possible.
- If clusters are removed manually, milkers need to have enough time to reach all cows before significant over-milking occurs (minimal if the mean overmilking time is less than 1 minute per cow; moderate if between 1 and 2 minutes per cow). Signs of continuous over-milking may indicate that the milker is handling too many clusters.
- Take care with newly calved cows, young cows with small teats, and cows on test buckets as they are especially susceptible to injury through over-milking.
- Watch for cows kicking at the clusters and teat end damage as these can indicate that cows are being over-milked.
- Avoid using weights or machine stripping slow milking cows - it leads to over-milking of the other cows.
- Incomplete milking:
- Incomplete milking is defined as having more than 20% of quarters with greater than 250 ml of milk that can be stripped out by hand after milking.
Automatic cluster removers
Automatic cluster removers (ACR) can boost productivity per milker in both rotary and herringbone dairies. Working conditions are also improved by reducing cluster handling requirements.
A large percentage of New Zealand’s dairy cows are regularly over-milked resulting in reduced milking speed, poor udder health, and cow discomfort. ACR are designed to remove a cluster from individual cows at a pre-determined end point of milking and can provide a solution to these issues.