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In the past, there were few differences between individual milking machines. But huge genetic variation between dairy breeds has led to significant variation in milk yield, milk flow rates, teat size and teat shape.

The range of milking strategies across different herds is also broader than ever.

This means a one-size-fits-all approach is no longer appropriate, and milking machine performance needs to be adjusted to reflect each individual farm’s situation.

See also: How teat health can be used to evaluate milking performance

To establish specific priorities for machine milking, the first step is to assess current performance:

Herd priorities will vary, but may include shortening unit-attachment time, reducing teat-end hyperkeratosis or teat oedema, improving cow behaviour – less kicking or fidgeting – and eliminating liner slip.

Factors other than machine settings may limit performance or even make certain forms of machine optimisation counterproductive. They include:

A pragmatic approach to achieving milking priorities may be needed where these limitations apply.

Conversations about vacuum often refer to system vacuum or the figure displayed on the vacuum gauge.

However, to give a reliable indication of vacuum at cow level, the vacuum inside the short milk tube of the liner needs to be measured during milking.

The short milk tube vacuum is affected by how much vacuum “reaches” the cluster (basically system vacuum minus losses) and how effectively the machine is at moving milk away from the cow.

Inefficient machines may have substantial drops in short milk tube vacuum when cows have very high flow rates.

The target short milk tube vacuum depends on liner choice, and each liner has an optimum working range.

Higher vacuums will promote higher milking speeds, but increase the risk of teat-end hyperkeratosis. Lower short milk tube vacuums increase the risk of teat oedema and slower milking speeds.

The key measure to consider is the resting phase (D-phase) of pulsation, with rate and ratio being set to achieve the appropriate D-phase length.

Minimum D-phase recommendations are often based on theoretical “perfect” conditions. In practice, a minimum D-phase of 220ms is appropriate for most situations, being both safe and efficient.

Higher D-phases may be required to mitigate effects of drops in short milk tube vacuum in inefficient plants. And some liner types may require specific pulsation phase lengths.

Traditionally, automatic cluster removal (ACR) settings in the UK have promoted a very “dry” milking.

With more efficient parlours and faster-milking liners the resultant overmilking is a significant risk for teat-end hyperkeratosis and oedema.

When choosing a flow rate to trigger the ACR:

Milking units are commonly dragged off the udder while still under vacuum. This is uncomfortable for the cow and increases the chance of bacteria entering the teat at this point.

Tom Greenham is a director of Advance Milking, a consultancy service for all aspects of udder health and milking machine performance.

Advance Milking works with dairy farms across the UK and Ireland to optimise udder health, milk quality and milking efficiency.

Mr Greenham also provides research, training and independent support to the dairy industry internationally.

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