The California Mastitis Test

The California Mastitis Test (CMT, also known as the California Milk Test) is a simple indicator of the Somatic Cell Count (SCC) of milk. It works by using a reagent, which disrupts the cell membrane of somatic cells present in the milk sample; the DNA in those cells to reacting with the test reagent. It is a simple but very useful technique for detecting subclinical mastitis on-farm, providing an immediate result and can be used by any member of farm staff. It is not a replacement for individual laboratory cell count sampling, but has several important uses.
The advantage of the CMT over individual cow cell count results is that it assesses the level of infection of individual quarters rather than providing an overall udder result, enabling the problem quarter(s) to be identified. It also provides a ‘real-time’ result; laboratory testing provides a historical result as it can take days for lab results to be returned.
A special reagent for the test is sold as ‘CMT-Test’, but domestic detergents (‘washing-up liquid’) can generally be substituted, being cheaper and more readily available.
For example, A goat with subclinical mastitis does not have the typical swollen, painful udder or abnormal milk and can therefore go undetected as a source of infection. Occasionally, such goats with subclinical mastitis can shed bacteria in huge numbers causing the bulk tank Bactoscan test to spike. In these cases, the CMT can be used to help identify a goat shedding high numbers of somatic cells and contributing to a high bulk tank Bactoscan test.

Profitable use of CMT
When you test all lactating animals monthly and keep records, you can expect the following benefits:
• Early detection of inflammation so that:
• Laboratory testing can be done on inflamed quarters
• Treatment can be made promptly and effectively
• Udder damage can be minimized
• Milk losses can be reduced.
o Ability to base milking order on test results. This helps prevent the spread of infection.
o Indication of when treatment may be needed and whether treatment has been effective.
o Indication of when to dispose of an animal.
o Better, service from the veterinarian, because the history of udder health is available.
o Less cost for laboratory testing, because only inflamed quarters need to be tested.