From the NMC Newsletter "Udder Topics", August, 1998

The relationship between somatic cell count (SCC) and abnormal milk has been known for years. In 1910, in the Journal of Infectious Disease, Prescott and Breed wrote: "For some time sanitarians have felt that it was important to be able to determine the number of body cells in milk. Large numbers have been held to be undesirable in as much as such conditions seem to be associated with abnormal conditions of the udder."

It was 50 years later however, before action was taken on a national level to establish regulatory limits on milk somatic cell counts. Recognizing the need for a uniform mastitis control program, the 1963 National Conference on Interstate Milk Shipments (NCIMS) appointed the Abnormal Milk Committee to study mastitis problems and recommend a course of action.

At the 1967 Conference, the committee presented the Abnormal Milk Program, which was approved and incorporated into the Grade "A" Pasteurized Milk Ordinance (PMO). The program phased in a SCC limit of 1,500,000 cells/ml. Phase I, effective July 1, 1967, required that screening procedures for the presence of abnormal milk be made at the same frequency as bacteriological tests. Phase II, effective July 1, 1968, provided procedures for producer notification and farm inspection when SCC exceeded the limit. Finally, Phase III, effective July 1, 1970, added a penalty clause for non-compliance. Permit suspension occurred if SCC limits were exceeded three out of five times. It is interesting to note that the original recommendation by the Abnormal Milk Committee called for a SCC limit of 1,000,000 cells/ml; however, this was changed to 1,500,000.

Proposals regarding SCC limits have been brought before NCIMS several times. In 1975 there was discussion of reducing the limit, but the 1,500,000 standard was retained. Then, at the 1983 Conference, delegates approved a proposal to reduce the standard to 1,000,000 effective July 1, 1986. A proposal to further reduce the SCC limit to 750,000 was submitted in 1989, but no action was taken. In 1991 proposals were submitted to reduce the SCC to 750,000 and 500,000; final Conference action set the SCC standard at 750,000 effective July 1, 1993.

Other proposals to reduce SCC limits have been submitted since 1993. At the most recent Conference held in May 1997, a proposal to reduce the limit to 400,000 (which is the SCC limit in the European Union and many other major dairy countries) was defeated. The next NCIMS conference is scheduled for May 1999.