and not from individual cows. This is because testing of individual animals at each milking would be expensive, but it also means that milk from a sick cow is diluted and averaged down by the healthy animals. Recently technological advances have allowed the dairy producer to test animals individually for SCC at every milking. The huge bulk tanks at large farms are accommodating of more sick animals in the herd, without the sick animals affecting the overall milk quality rating. However many different state and governmental agencies (including FDA) inspect each load of milk delivered to the processing facility as well as the processing facilities themselves to ensure that all milk processed through those facilities is safe for all consumers. As discussed in the paper Guidelines for Using the DHI Somatic Cell Count Program: The results of many studies suggest that cows with SCC of less than 200,000 are not likely to be infected with major mastitis pathogens, but cows with SCC above 300,000 are probably infected (Smith, 1996). Herds with bulk tank SCC above 200,000 will have varying degrees of subclinical mastitis present. Data from the National Mastitis Council (1987) show that 6% of the [udder] quarters in a herd could be expected to be infected in a herd with a bulk tank SCC of 200,000. At 500,000 SCC, 16% of the quarters may be infected with a 6% reduction in milk production compared to a SCC of 200,000. In Canada, European Union, Australia, New Zealand, Switzerland, and some US states (e.g., Washington) the somatic cell count shall be not more than 400,000 cells per milliliter. The somatic cell count limit is 750,000 in the majority of the USA and 1,000,000 in Brazil. Bacteria in milk can come from sources other than the animal. Over time the milking pipeline and equipment can become coated with residues such as milkstone which are not removed by standard detergents and require periodic flushing of equipment with high strength corrosives. Automatic washing equipment for the bulk tank may not effectively clean all interior surfaces, and does not clean the exterior of the bulk tank at all. Milk processors and co-ops purchasing milk routinely award farmers for having the lowest possible SCC counts via "quality bonuses" added to each milk payment to the dairyman. See also Mastitis in dairy cattle Breed method References Dairy farming Cattle