A discussion of normal and abnormal milk based on somatic cell count and clinical mastitis

Mastitis is an inflammation of the mammary gland, generally caused by an intramammary infection, that results in altered composition of milk. The two primary means used by the industry for detection of mastitis are: 1) visual examination of the raw milk for clinical signs such as clots and flakes; and 2) the determination of the somatic cell count (SCC) of the milk. Somatic cell counts increase during inflammation. When clinical signs of mastitis are observed in quarter milk, the milk is by definition abnormal. There is no single SCC that can be said to be the dividing line between normal and abnormal milk. However, most mastitis research workers would agree that the SCC of normal, healthy quarters will be less than 100 000 cells/ml of milk and that SCC greater than 200 000 is indicative of the presence of inflammation, infection and reduced manufacturing properties.