The California mastitis (CMT) test is a simple procedure to help identify high somatic cell count (SCC) quarters within high cell count cows.

The CMT kit is an excellent tool to help identify high SCC quarters within high cell count cows. It is impossible to identify sub clinical mastitis without an aid, as there are no visible clots in these high cell count quarters to the naked eye.


  1. The procedure is very simple, you should carry out the test prior to milking;
  2. Discard the first three draws and then fill each well with a quantity of milk, try to avoid cross contamination;
  3. Once all four wells have a quantity of milk, tilt the tray to a 45º, this will ensure there is an equal volume of milk in all four wells;
  4. Turn the tray back flat and squeeze the bottle until an equal quantity is applied to all four wells; there should be approx. 50:50 mix of milk and reagent;
  5. Stir the tray for 30 seconds and watch for any changes to the consistency of the solution. The degree of thickness reflects how high the SCC level is within the quarter.

Teagasc recommends you take a sample of milk into a sample bottle and label them and wait until the end of milking before you test the cows, when you have time to analyse and record your results.

Scoring scale

The accurate interpretation of this rapid test takes a certain level of skill and practice. The starting point should be to have a recent milk recording carried out or an individual SCC on all cows carried out by your co-op.

To help train your eye in, you should consider carrying out a SCC test on individual quarters, then carry out an CMT on these quarters and compare results.

Score 1 – Very good – no change to the thickness very fluid – SCC<500,000;

Score 2 – Poor – slight changes to consistency grains evident when tilted left to right, slight thickness evident – SCC >500,000 and <1,500,000;

Score 3 – Very poor – thickness very evident when swirling, when emptying wells solution may stick to the paddle – SCC >2,000,000.

It is very important to record the results. When the results are recorded you can analyse them to see if any pattern is evident, if milking through the back legs, it may suggest a contagious mastitis which may be spread through the liners.

It is important to discuss with you adviser or vet what treatment / culling procedures should be followed when you have performed this test.

These results in conjunction with a milk recording are an excellent tool to control and understand mastitis patterns within a dairy herd.