Milking machine and mastitis [Longread]

The milking machine is unique as it harvests food from a living animal on a regular basis. It must work very efficiently so that cows are milked swiftly with minimal effects on udder health. It is essential that teat heath is not compromised. You cannot afford to have cows leaving the milking parlour with milk remaining in their udder because the machine was not working correctly.

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The milking machine is often neglected compared to other pieces of machinery on the farm. Most farmers are good about servicing their tractors but the milking machine might only be serviced once or twice a year, irrespective of how many hours of use it has carried out.

The milking machine can increase the risk of mastitis in several ways including damage to the teat canal, damaging teat skin, teat congestion, hyperkeratosis and liner slip. It is important to ensure that every milking machine is not contributing to mastitis problems.

1. Damage to the teat or teat canal

A poorly functioning machine can increase teat damage resulting in more mastitis and higher cell counts. The teat canal is the main defence mechanism to keep bacteria out of the udder. It is between 6 and 10 mm long and has interdigitating folds which close when the cow is not being milked.

One of the most common forms of damage is hyperkeratosis where there is excess keratin production and this keratin protrudes from the teat-end. Keratin lines the teat canal, has antibacterial properties and helps trap bacteria as they try and enter the udder.
Hyperkeratosis can be a machine induced problem and can be caused by high vacuum levels, poor pulsation settings or overmilking (leaving the units on after the cow has finished milking or putting the unit on too early when milk let-down has not started). Cows with pointed teats are more prone to hyperkeratosis than those with cylindrical or square teats. Hyperkeratosis can be influenced by environmental conditions, weather and milking management.

Bacteria, especially Staph aureus and Strep dysgalactiae, can colonise teats with poor skin condition. If the teat skin is rough this will also harbour dirt. Teats with ingrained dirt are more difficult to clean and this will increase the risk of clinical mastitis.

Teat scoring is carried out immediately after unit removal and can quantify levels of hyperkeratosis, congestion, oedema etc. The greater the level of hyperkeratosis, the greater the risk of mastitis occurring. Teat scoring should be carried out on a regular basis to monitor teat health and skin condition.

Figure 1 – shows the proportion of teats with subclinical mastitis as measured by the CMT (California Mastitis Test). HK0 is a healthy teat and HK5 is the most severe hyperkeratosis. This shows that the proportion of high SCC quarters increases with severity of hyperkeratosis.

Teat damage is less likely to occur in modern milking machines which are designed for fast milk flow rates and a short milkout time. Modern machines use automatic cluster removers, commonly referred to as ACRs which are adjustable and accurate so that cows are less likely to be overmilked. High vacuum levels can increase the risk of teat-end damage, especially when cows are overmilked.

Figure 2 – shows that the number of cases of clinical mastitis more than doubled in October when the vacuum level increased to 55 kPa. This occurred due to a blocked regulator air filter (see Photo 11) which was not able to drop the vacuum in the parlour. Cows were unhappy being milked and teats congested. Once the vacuum level was corrected the number of cases dropped back to normal and cows were happy coming in for milking.

Effective pulsation is required to avoid teat damage. ISO standards require the massage or ‘d’ phase to be a

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