The California Mastitis Test (CMT) is a simple cow-side indicator of the somatic cell count

Somatic cell count

Somatic cell count is an indicator of the quality of milk. Somatic cells are leukocytes . The number of somatic cells increases in response to pathogenic bacteria like Staphylococcus aureus, a cause of mastitis. The SCC is quantified as cells per ml...

 of milk

Milk

Milk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to the baby and can reduce the risk of many...

. It operates by disrupting the cell membrane

Cell membrane

The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...

 of any cells present in the milk sample, allowing the DNA

DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 in those cells to react with the test reagent, forming a gel

Gel

A gel is a solid, jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state...

. It provides a useful technique for detecting subclinical mastitis

Mastitis

Mastitis is the inflammation of breast tissue. S. aureus is the most common etiological organism responsible, but S. epidermidis and streptococci are occasionally isolated as well.-Terminology:...

.

Development

Whiteside described a reaction between sodium hydroxide and milk that resulted in the thickening of mastitic milk. The utility of this reaction as a field test was limited by the fact that the reaction was sometimes difficult to observe, and would eventually occur even in normal milk. A refined version of the test, which enhanced its sensitivity, and eliminated the confounding effect of milk fat, uses an anionic surfactant

Surfactant

Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid...

, which forms a gel with the DNA

DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 in somatic cells in the milk

Use

A four-well plastic paddle is used, one well being for each quarter of the cow to be tested. Foremilk is discarded, and then a little milk drawn into each well. An equal volume of test reagent is added, and gently agitated. The reaction is scored on a scale of 0 (mixture remains unchanged) to 3 (almost-solid gel forms), with a score of 2 or 3 being considered a positive result. A special reagent for the test is marketed under the name 'CMT-Test', but domestic detergents are frequently used instead, being cheaper and more readily available. Fairy Liquid is as suitable as a reagent for the CMT, although many cheaper detergents are not