Yes, individual cows with counts of 20,000 cells per milliliter or less may be more susceptible to E. coli infections, according to research by scientists in the Netherlands and Great Britain. That’s because there are fewer immune cells, initially, to fight off the bacterial onslaught.

But having SCC too low is not a problem for most dairies. To have individual cows down around 20,000, the herd average would have to be something like 50,000, and very few herds achieve that. “The majority of our herds could very safely reduce cell counts without increasing the risk for clinical mastitis,” says Ruth Zadoks, veterinarian with CornellUniversity’s Quality Milk Production Services.