Somatic cell counting

As part of licensing to make farmstead goat’s milk cheese, our goat’s milk will be regularly sampled by an inspector and the somatic cells counted.

Somatic cell count (SCC) is an indicator of the quality of milk. Somatic cells in cow’s milk are solely white blood cells. The number of somatic cells increases in response to pathogenic bacteria like Staphylococcus aureus that cause mastitis. The New York State milk standards require less than 750,000 somatic cells/ml in cow’s milk.

However, somatic cells in goat’s milk are not only white blood cells but also cytoplasmic particles and a small number of epithelial cells from milk secreting tissues. While mastitis can increase counts in goats, other non-infectious factors will also increase counts in goat’s milk. Some of these are parity (previous number of births), season, advanced lactation and injury. The New York milk standard for goats accounts for these other factors by requiring less than 1.5 million somatic cells/ml in goat’s milk, double that of cows.

Additionally it is terribly important that the right stain be used on the goat’s milk sample. Typically a “blue” stain is used by laboratories to stain the cells being counted. Because somatic cells in goat’s milk can also be epithelial cells from milk secreting tissues and cytoplasmic particles, these can be confused with somatic cells from infection. Only the “green” stain (Pyrorin Y-methyl green stain) distinguishes between these types of somatic cells.

At our inspector’s suggestion, we recently “pretested” our goat’s milk to see where we stood, especially considering that we are at the tail end of lactation. If the results exceeded 1.5 million, she suggested drying off the goats and complete the licensing process when the goats freshen with a milk sample from the beginning of lactation. In order to get the “green” stain we had to send the sample to Eastern Lab Services in Waverly, Pennsylvania. We are happy to report that that our count was 660,000, well below even cow standards!

(Picture is a non infectious somatic cell in goat’s milk – a cytoplasmic particle shed from the epithelia lining)

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