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Dairy farming special: Understanding the importance of controlling thermodurics

As some milk processors are beginning to introduce routine testing for thermoduric bacteria in milk, Hannah Park looks at some top-tips for reducing levels on-farm.

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Dairy farming special: Understanding the importance of controlling thermodurics

Monitoring bacteria levels in milk has been done using bactoscan figures for many years, but measuring specifically for thermoduric bacteria, the heat-resistant bacteria capable of surviving pasteurisation, is increasingly moving up the agenda.


With some milk processors beginning to introduce routine testing of their supplier pools in the last 12 months to use within payment parameters, farmers may want to take steps to monitor and manage thermoduric bacteria levels in milk.


Andrew Henderson, director and vet at Lambert, Leonard and May, posed a number of questions around thermodurics during a recent webinar on the topic and offered some tips to manage thermoduric counts in milk.


What are thermoduric bacteria and how do they manifest in food?


Thermodurics are heat-resistant bacteria with the ability to survive pasteurisation, providing them an opportunity to manifest in food products and potentially cause shelf life, quality and food poisoning issues.


Some of these bacteria will continue to grow at temperatures lower than 7degC, meaning they have the potential to multiply in milk on the supermarket shelf.


High thermoduric counts can manifest in finished products in many ways and can be attributed to causing ‘off’ flavours in milk and cream, as well as impacting certain types of cheese and butter production.

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What are the targets when it comes to thermoduric counts?


Thermoduric testing is on the rise, with some milk processors introducing testing to their payment schedules in the last 12 months.


Counts of more than 1,000 colony-forming units (cfu) per ml are generally recognised as a chronic failures in cleaning. However, levels of greater than 500cfu/ml indicates a look at plant hygiene and plant management on-farm is needed to deal with thermoduric bacteria prevalence.


Suggested internationally recognised ‘normal’ standards are set as below 175cfu/ml, with ‘excellent’ at below 10cfu/ml.


What can thermoduric counts on-farm tell us?


Thermoduric counts give a good general indication of milking equipment sanitation and a measure of whether a farm is experiencing hygiene failures.


Research suggests thermoduric bacteria prevalence was higher in August to September, with some data showing a peak in February and March.


Farms which ordinarily have consistently low thermoduric counts over a period of time could sometimes experience elevations as a result of these seasonality changes, and generally these subside again in the following month’s test.

Andrew Henderson
Andrew Henderson

Have thermodurics been used as a quality measure before?


Yes, thermoduric bacteria is not a new issue. It has been recognised as a milk quality issue since the early 20th century and is already being used within payment parameters worldwide in New Zealand, Ireland and the Netherlands.


When it comes to export markets for products such as milk powder, there are stringent requirements for standards, including thermodurics.


Why is it important to manage thermoduric counts?


Thermodurics can be an issue in infant milk formula, as levels have the potential to increase if the product is not stored correctly and there is some concern around its ability to cause food poisoning.


With this in mind, it is important thermoduric levels are as low as possible when milk leaves the farm, so an understanding of possible sources of thermoduric bacteria is needed.


Where do thermoduric bacteria come from?


It is important to recognise that thermoduric bacteria are not shed directly into milk, they get into milk as a result of poor cow cleanliness or poor teat hygiene, which then allows a route for bacteria into milk.


Thermoduric bacteria can be present in a range of environmental sources, including soil, bedding, feeds and forage, dust, water and faeces. Sources of thermoduric contamination in milk on-farm could be through dirt on teats, from soil or contaminated faeces as a result of bacteria in feed.


Contaminated milk will pass through milking equipment, so failure to clean this can then act as a reservoir for infection to continue to contaminate milk in the tank.

Tips to manage thermoduric bacteria

THERMODURIC bacteria counts are derived from a wide-range of sources, so environmental management is key when it comes to managing levels:




■ Cow cleanliness: This is one of the first things to look at if experiencing high thermoduric counts and, if there is an issue, consider using hygiene scoring to allow drill down into where most contamination is on cows.


For example, most contamination on the legs is likely from faecal splashing in alleyways, the tail from poor or small cubicle design, or on flanks from poor bedding management.


■ Trimming: Tidying up the tail or udder region routinely to remove hair also removes much of the ability of bacteria to stick to these regions.




■ Clean parlour: Ensure clusters do not become detached during cleaning and clean them between reattachments.


■ Staff hygiene: Those milking should be keeping themselves clean during milking, wearing clean gloves and keeping outerwear and arms clean.


■ Teat preparation: There are a number of studies which suggest effective teat preparation is key to managing thermodurics effectively.


One showed a 96 per cent reduction in thermoduric levels in milk by using treatment and drying in comparison to using no treatment at all.




■ Residue left in pipes after milking: Residue is generated inside plant fixtures by milk and water going through the lines which forms an effective environment for thermoduric bacteria to reside in and end up in milk.


The use of a caustic (alkaline) detergent is effective for fat and protein removal (from milk) alongside an acid-based cleaner to control water residue, with an alternative acid and alkaline washing recommended on a daily basis to control thermoduric levels.


■ Cleaning external pipes: Ensure adequate water temperature for washing (looking at water temperature at boiler entry and exit to parlour, as well as during main circulation in the milk line) and ensure air injectors are working correctly and cleaned periodically.

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