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johnes testing

Johne’s Disease

  • Johne’s causes decreased milk production, chronic diarrhea, and death.
  • Contagious, chronic, and usually fatal infection that primarily affects the small intestine of ruminants.
  • Signs of Johne’s in cattle include weight loss and diarrhea with a normal appetite but are rarely evident until two or more years after infection.
  • The causative bacteria is Mycobacteria avium subspecies paratuberculosis (MAP), and transmission is primarily fecal/oral to calves less than six months of age.
  • According to 2007 Dairy NAHMS study, about 68 percent of U.S. dairy herds have at least one cow that tests positive for Johne’s with herd prevalence approaching 100 percent in large dairy herds.

Sample Type(s)

  • Milk
    • Fresh, frozen or preserved
    • Individual or bulk tank
    • Pooling available for PCR test
  • Serum
    • Fresh
  • Feces
    • Fresh or frozen. Pooling available – up to 5 samples per test


  • Test milk or blood at dryoff or in early lactation
  • Test fecal samples at any age


  • Milk and blood ELISA available within 5 days of sample receipt
  • PCR (milk or fecal) available within 10 days of sample receipt
  • Reported as Positive, Negative or Suspect
Test Type Positive Negative Suspect
Milk ELISA >0.3 <0.2 0.2 – 0.3
Bulk Milk ELISA >0.1 <0.1
Blood ELISA >0.55 <0.45 0.45 – 0.55
Bulk Milk PCR <41 >41
Fecal PCR <38 Undetected 38 – 40
Test Type Positive Negative Suspect
Blood ELISA >0.55 <0.45 0.45 – 0.55


  • Animals with a Suspect result should be retested at a later date.
  • Animals that are within 7 days of freshening have a high probability of giving false positive results when tested because of the presence of colostral antibodies.


  • Individual ELISA (milk, blood) $6.50/sample
    • Multiple test discounts! $11 for two ELISAs on the same sample; $15.00 for 3 ELISAs
  • PCR (milk, pooled, or bulk milk) $50/test
  • PCR (fecal) $40/test
  • PCR (pooled fecal) $12/test; minimum 3 samples, maximum 5 samples
  • Testing billed upon sample receipt
  • $10 sample submission fee per order

Submit Samples

Additional Resources

Been there, done that. What's next for Johne's disease?

Dr. Don Niles, Dairy Operations Manager, Pagel’s Family Businesses, and Dr. Scott Wells, Professor in the Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, discuss practical approaches to level up your herd’s Johne’s management.

CentralStar Laboratories

CentralStar’s Laboratories provide sample analyses on milk, blood, fecal, and tissue samples for a variety of production, disease and health-related traits.

More than 5.3 million samples are processed annually using state-of-the-art equipment and techniques including infrared spectroscopy, flow cytometry, ELISA, PCR, and more.

Testing Supplies

For convenience, shippers and sampling supplies can be purchased online.

Diagnostic tests are intended to identify diseases in the cow for their health, and do not determine the “safety” of milk. Testing prices listed effective 10/1/2020. 

How To Collect a Blood Sample for Serum Tests

Supplies Needed:

  • Vacutainer® Vial
  • Double-sided needle
  • Needle holder

Be sure to check which type of vial is required for your desired test type.

  • Red-top vials: Pregnancy, Johne’s, Leukosis, BVD and Neospora.
  • Purple-top vials: A1/A2 and BLV SSI PCR.
test step 1

Step 1:

Screw needle into needle holder
Insert the Vacutainer vial into the holder
DO NOT puncture the vial stopper

test step 2

Step 2:

Lift the tail straight up and clean area
Find the midline groove 4 to 6 inches from the base of the tail
Insert the needle about ¼ inch into the groove, perpendicular to the underside of the tail

test step 3-4

Step 3:

Engage the vacuum by pressing the vial up puncturing the stopper
If blood does not flow, carefully redirect the needle
DO NOT remove the needle from the tail

Step 4:

Once blood begins to flow maintain needle position
Collect a minimum of 4cc of blood

test step 5

Step 5:

Disengage the vial from the holder BEFORE removing needle from the tail

test step 6

Step 6:

Clearly label vials with animal identification
Fill out a sample submission form

Step 7:

Keep vials at room temperature to allow clotting (1 to 2 hours)
Once clotted, keep samples refrigerated until submitted to the lab

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