On-farm labs are a valuable and economical tool for raw dairy farmers
The three pillars of the Raw Milk Institute’s (RAWMI) Method for safe, low-risk raw milk are 1) farmer mentoring, 2) risk management plan for each farm, and 3) regular bacterial testing of raw milk. This method works well and has been documented to lead to a significant reduction in raw milk-related illnesses and outbreaks. Researchers who have studied the safety of raw milk produced with the RAWMI Method have concluded that “raw milk can be produced with a high level of hygiene and safety.”
RAWMI’s farmer mentoring program and assistance in developing an individualized risk management plan are free for all farmers. However, milk testing costs can be an ongoing financial burden which make small-scale farmers hesitant to test their milk often. But there is a great solution to this: on-farm testing!
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What is an On-Farm Lab?
Pioneered by Edwin Shank from The Family Cow dairy in Pennsylvania, on-farm labs are a tremendous resource for dairy farmers. On-farm labs can be set-up on the countertop in a small, clean workspace. Once the lab area is ready, farmers can easily test their milk for coliforms and Standard Plate Count with the use of a small incubator.
Set-up costs for on-farm labs are in the range of $800-$1,000. RAWMI is currently offering grants of up to $500 to offset lab costs for farmers who are Listed or going through our Listing program. After the initial set-up costs, raw milk testing costs are only $1-$3 for each test performed in the on-farm lab.
Benefits of On-Farm Labs
On-farm labs have numerous benefits for raw milk farmers. As RAWMI Chairman Mark McAfee says, “What gets measured gets done.” Ignorance is not bliss when it comes to raw milk. Testing allows farmers to dependably produce low-risk raw milk with confidence.
With on-farm labs:
Farmers can test their milk for coliforms and Standard Plate Count (SPC).
Ongoing testing costs are only $1-$3 per test.
Farmers can inexpensively test their milk as often as desired, so they can identify patterns in their bacterial counts which help in identifying trouble spots ahead of time.
The effects of new equipment or procedures on bacterial levels can be evaluated.
Farmers can test more often as needed for troubleshooting high bacteria counts.
Annual water tests can also be performed.
Which Tests You Can Perform in an On-Farm Lab
The bacterial tests performed in an on-farm lab (coliform and Standard Plate Count) are used to provide a general indicator that the milk is being produced in a way that is unlikely to lead to pathogens and pathogen growth.
The RAWMI Common Standards aim for a rolling three-month average of:
<5,000 cfu/mL for SPC
<10 cfu/mL for coliforms.
NOTE: RAWMI does not generally recommend on-farm testing for specific pathogens (such as E coli 0157:H7, salmonella, listeria mono, etc), due to potential hazards from accidental release of pathogens on the farm. Specialized test systems are being developed for on-farm testing of pathogens. In those systems, the test samples are destroyed after each test. Those test systems are stand-alone, may be cost-prohibitive for small-scale farmers, and are not discussed further in this article.
Materials for Building Your Lab
general list of supplies
Standard Plate Count and Coliform Count testing discs (either petri-films from Neogen or peel-plates from Charm Sciences)
Sterile pipettes (individually wrapped)
Sterile water
Incubator that will maintain at 90 F / 32 C
Lightbox, magnifier, and spreader (if using Neogen testing discs)
NOTE: Standard Plate Count (SPC) is also known as Rapid Aerobic Count (RAC), Aerobic Count (AC), and/or Aerobic Plate Count (APC).
Neogen vs Charm Sciences testing Systems
There are currently two different systems for performing on-farm testing, developed by Neogen (formerly known as 3M) and Charm Sciences. Both of these systems work well for on-farm raw milk testing. The basic lab equipment (incubator, pipettes, sterile water, etc.) is the same with either system.
Neogen’s testing system uses petri-films and provides results in 24 hours for both coliforms and SPC. Unopened packages of Neogen petri-films are stored in the refrigerator or freezer for up to 18 months, with opened packages being stored at room temperature for up to one month.
Charm Sciences testing system uses peel-plates and provides coliform results in 24 hours and SPC results in 48 hours. The peel-plates can be stored at room temperature for up to 12 months. Testing costs are currently a bit lower with Charm Sciences peel-plates than with Neogen petri-films.
VIDEO COMPARISONS:
NOTE: Charm Sciences has two options for coliform testing. The basic Coliform Count test peel-plates are fine to use, as are the E Coli and Coliform Count EC peel-plates (which have different colored dots for E. coli bacteria).
E. coli is a large family of bacteria of which most are NOT pathogenic. The Charm Sciences EC peel-plates do NOT give an indication of the presence of specific pathogenic bacteria. Furthermore, some pathogenic E. coli do not result in the color-change dots on the Charm Sciences EC peel-plates. Nonetheless, some farmers find these plates helpful to use as presence of E. coli on the plates can help with determining the source of the bacteria in the milk (such as environmental contamination).
Materials Lists for Testing with Charm Sciences or Neogen
Charm Sciences Peel-Plate Materials List from Kelsey Barefoot (RAWMI Board Member and owner of The Barefoot Cow Dairy): 2-page materials list for performing on-farm testing with Charm Sciences peel-plates
Raw Milk Lab Materials List from Edwin Shank at The Family Cow Dairy: Short 1-page list of materials required for performing on-farm testing with Neogen (3M) Petri-Films
How to Test Your Milk
GENERAL TESTING PROCEDURE
Turn on the incubator to 32 degrees C / 90 degrees F.
On a clean surface, prepare the milk samples for testing with petri-films or peel-plates.
For coliform count, you will test the milk “neat” (undiluted).
For SPC testing of clean, well-produced milk, a 1:10 dilution will generally work best.
Using a clean pipette for each test, squeeze the milk or diluted milk onto the peel-plate or petri-film.
Place the testing discs in the incubator for 24-48 hours (depending on which testing discs are used).
Remove the testing discs from the incubator and count the dots to determine your results.
Detailed Testing Procedures
RAWMI VIDEO: How to Test Raw Milk with Charm Sciences Peel Plates
Charm Sciences Peel-Plate Procedures from Kelsey Barefoot (RAWMI Board Member and owner of The Barefoot Cow Dairy): 2-page procedures for performing on-farm testing with Charm Sciences peel-plates
Raw Milk Lab Procedures from Edwin Shank at The Family Cow Dairy: Short 2-page list of procedures for on-farm lab testing with Neogen (3M) Petri-Films
On-Farm Lab Testing: A Guide to Raw Milk Bacteria Testing from Jenny Skelonc at Six S Dairy: Comprehensive 20-page guide to on-farm testing with Neogen (3M) Petri-Films, including materials list, procedures, results interpretation, and tips for success
How to Interpret Your Results
BASIC PROCEDURE FOR interpreting test results
Remove the testing discs from the incubator.
Count the dots on each plate.
For coliform count test, your result is the number of dots.
If you used a dilution for the SPC test, such as 1:10, make sure to multiply the number of dots by your dilution factor.
For example, if you counted 31 dots on your SPC test and used a 1:10 dilution, multiply 31 X 10 = 310 cfu/mL for your SPC.
Record your results.
Detailed Resources for Interpreting Your Test Results
