California milk test for dairy cows

By testing each quarter individually, the California milk test (CMT) can indicate which quarter has a raised cell count. This test can help to detect mastitis.

Managing calving around drying-off

What is a California milk test (CMT)?

The test uses a reagent that is added to a sample of milk. If the test is positive and a quarter is infected, the CMT mixture will appear thickened and gel-like.

Equipment needed:

  • CMT paddle
  • Gloves
  • Reagent
  • Recording sheet

How to do the California milk test (CMT)


Should any of the rings appear thickened and gel-like, this indicates a positive test.

Watch our short film which shows how to perform a CMT, along with the results that might be seen.

Grading reactions to CMT

Rather than just ‘positive’ or ‘negative’, the CMT reaction can be graded on a scale of 0–3. With experience, a user may also be able to estimate the SCC (although this is by no means an accurate determinant).

Useful links

Managing mastitis

Mastitis control plan