Ed DePeters, Animal Scientist, UC Davis; Jennifer Heguy, Dairy Advisor, UCCE Stanislaus & San Joaquin Counties: Field Notes

Milk quality starts on the farm. The processing plant cannot improve the quality of your milk; it can only maintain the quality that you deliver. In a recent article we talked about preparing cows in the milk parlor. (Read it online). In this article, we‘ll continue the discussion of producing quality milk by explaining your milk laboratory results and highlighting reasonable goals for your dairy.

Quality standards for market milk (Grade A):

Standard plate count (maximum): 50,000 bacteria per milliliter of milk

Laboratory pasteurization count (maximum): 750 bacteria per milliliter of milk

Coliform (maximum): 750 bacteria per milliliter of milk

Somatic cell count (maximum): 600,000 cells per milliliter of milk

What do these standards refer to?

Standard Plate Count (SPC) is a measure of the bacteria present in bulk tank milk. Basically, a sample of milk is plated and the number of colonies counted. It is an estimate of the total aerobic bacteria (those which can live in the presence of oxygen). High SPC may indicate inadequate refrigeration, but it is not an indication of udder health (mastitis). A goal may be to have a SPC of 5,000 or lower.

Laboratory Pasteurization Count (LPC) is the cell count of bacteria after a raw milk sample has been lab pasteurized. It is similar to the SPC except the milk is pasteurized. The organisms that survive pasteurization and grow on the plate most often originate from the soil environment. High LPC indicates improper cleaning procedures. Check the cleaning procedures so that there are no residues in the pipeline, traps, and tank. Check the temperature of the wash water during the wash cycle. Check the quality of the soap and cleaning chemicals. Check the cow preparation in the milking parlor so there is no feed, dirt, feces, or other foreign organic material on the teats and udder that will contaminate the milk. An-other potential cause of high LPC is long milking shifts. In-line filters should be changed out as appropriate if milking lasts longer than four hours. A high LPC is not an indication of general udder health (mastitis). A goal may be a LPC of 100 or less.