Understanding Thermoduric Downgrades

Summary:

Here you’ll find key causes of thermoduric bacteria and simple steps to prevent milk quality downgrades.

Thermoduric bacteria are heat-resistant bacteria that can survive pasteurisation. Early action is the best way to prevent thermoduric downgrades.

Downgrade support

Your milk quality results are available daily on your tanker docket or on the Farm Source website.

If your thermoduric milk quality result is “Quality” (500-1,499 ml), a “0” result or if you receive a “thermoduric alert”, you should carry out an immediate plant and vat hygiene check to mitigate against any potential future milk quality downgrade.

Organise a traceback

If you cannot determine the cause of the test result or you receive downgrades, call the Farm Source Service Centre.

Depending on the duration and severity of the issue, they will organise an on-farm trace back and take you through the Milk Quality Support Programme.

A snapshot of what to look for:

  • Check for build-up in the silo, milk line, and plant caused by poor cleaning
  • Check all rubberware for wear, damage, or ageing
  • Ensure jetters and pulsators are working properly with good flow and turbulence
  • Follow the full wash programme, including temperature, chemicals, and timing
  • Check silage quality and watch for spore alerts on tanker dockets
  • Look for a rainbow or dull film on silo surfaces as the protein deposit develops
  • Check for light brown, soft coating like varnish by scraping build-up with your fingernail

How to prevent thermoduric downgrades

Early intervention is the best tool you have to prevent thermoduric downgrades.

Prevent protein deposit build-up by:

  • Use enough hot water: 10L per set of cups and at least 2–4% of vat capacity
  • Wash with alkali at least twice a week, more often in summer
  • Keep wash temperature at 80–85°C and empty before it drops below 55°C
  • Use the right detergent amount as per the label
  • Run the wash for at least 5 minutes to ensure proper cleaning

Be sure to replace rubber-ware as per manufacturer’s recommendations.
 

Carry out regular plant and vat hygiene checks:

  • Use the Dairy Diary app to make filling out your Monthly Plant Check Assessment easier and faster
  • Follow diagrams and prompts on what you should be checking
  • Record notes as you go through checks
  • Use the farm summary to see what’s done and what’s left
  • Access more information on the Dairy Diary app

Make sure that you complete the monthly milking plant hygiene assessment in your Dairy Diary app or in the physical book.

Poor quality silage – look for the spore alert on your daily docket.
 

General recommendations:

  • Do not feed the gunge layer (top) from an open silage pit or other water damaged grass crops
  • Prevent manure ponding of stock races, holding or feed pad areas
  • Do not wet udders at milking time

Testing time and results

  • Test takes 4 days, with most growth in the last 24 hours
  • Early warning if counts go over 1000 cfu/ml at 42 or 72 hours
  • A 0 result means no thermoduric bacteria was detected
  • No result may mean bacteria levels were too high to count (“spreader”)
  • Contact Farm Source team if you get a spreader result

Why are there sharp rises in thermoduric downgrades before and after Christmas? 

  • Expect higher risk in warmer months as bacteria grow faster
  • Watch for build-up forming after winter cleans as the season progresses
  • Check plant and vat more often as temperatures rise
  • Increase alkali wash frequency from November onwards