the regulations related to milk can be found on this site: http://www.access.gpo.gov/cgi-bin/cfrassemble.cgi?title=200621So I went to the aforementioned website and didn't find anything regarding pus or somatic cells, but after doing a little more digging on Google, I found someone else who had the same question on Google Answers.
use the search term to find milk requirements.
You can go to the link to read the full answer, but I've included some interesting parts:
Cells from the body that compose the tissues, organs, and parts of that
individual other than the germ (sex) cells.
The Somatic Cell Count and Milk Quality
"The somatic cell count (SCC) is commonly used as a measure of milk quality. Somatic cells are simply animal body cells present at low levels in normal milk. High levels of these cells in milk indicate abnormal, reduced-quality milk that is caused by an intramammary bacterial infection (mastitis). The majority of the cells in a somatic cell count are leukocytes (white blood cells), and some are cells from the udder secretory tissue (epithelial cells). The epithelial cells are part of the normal body function and are shed and renewed in normal body processes. The white blood cells serve as a defense mechanism to fight disease (infection), and assist in repairing damaged tissue. Milk markets routinely rely on somatic cell counts to help ensure a quality product. SCC levels are monitored to assure compliance with state and federal milk quality standards. Today, most markets pay a premium for low SCC, good-quality milk."
Table 1. Chemical, Physical, Bacteriological, and Temperature Standards
GRADE "A" RAW MILK AND MILK PRODUCTS FOR PASTEURIZATION, ULTRA-PASTEURIZATION OR ASEPTIC PROCESSING
Cooled to 10°C (50°F) or less within four (4) hours or less, of the commencement of the first milking, and to 7°C (45°F) or less within two (2) hours after the completion of milking. Provided, that the blend temperature after the first milking and subsequent milkings does not exceed 10°C (50°F).
Individual producer milk not to exceed 100,000 per mL prior to commingling with other producer milk. Not to exceed 300,000 per mL as commingled milk prior to pasteurization.
No positive results on drug residue detection methods as referenced in Section 6 - Laboratory
Somatic Cell Count*...
Individual producer milk not to exceed 750,000 per mL.
GRADE "A" PASTEURIZED MILK AND MILK PRODUCTS AND BULK SHIPPED HEAT-TREATED MILK PRODUCTS
Cooled to 7°C (45°F) or less and maintained thereat.
20,000 per mL, or gm.***
Not to exceed 10 per mL. Provided, that in the case of bulk milk transport tank shipments, shall not exceed 100 per mL.
Less than 350 milliunits/L for fluid products and other milk products by the Fluorometer or Charm ALP or equivalent.
No positive results on drug residue detection methods as referenced in Section 6 - Laboratory Techniques which have been found to be acceptable for use with pasteurized and heat-treated milk and milk products
******I recommend going to the above site to see the full Milk Ordinance table*******
A Somatic Cell Count (mostly white blood cells) is not tested in pasteurized milk because it is tested "at the farm gate". Milk will never be 100% free of somatic cells because they are a normal part of lactation. However, taking a Somatic Cell Count is important because a high count will effect the quality of the product (off flavor,color, and smell plus a reduced shelf life). A dairy farmer's raw milk collection cannot exceed a somatic cell count of 750,000 per mL at the farm gate. Cell count is determined by the health of the animals and the milk from one cow with mastitis (udder infection) will have a very high cell count, however, that cell count will be diluted when added to the rest of the herd's milk. The farm's milk is added to a truckload of milk from other farms which will dilute the cell count per mL further, and then that truckload is added to all the other truckloads at the dairy processing plant, diluting the cell count even further. Therefore, by the time the milk is bottled up, the milk will contain a somatic cell count of no more than 750,000 per mL and likely a lot less. Pasteurization is used to lower bacterial levels and not to reduce the somatic cell count.
So there you have it, ladies and gents. Milk, all milk and not just chocolate milk, has blood in it.