When using bulk tank samples to identify the presence of Staph aureus in the herd, you need to take more than one sample, says Charlene McLauchlan, technical services veterinarian with Monsanto Dairy Business.

Cows with Staph aureus don’t necessarily shed the bacteria at every milking. And, depending on your herd size and how often the milk is picked up, bacteria from infected cows may not be in the particular tank you sample. That means if you want to use bulk tank samples to identify if Staph aureus is in your herd, you need to collect samples for three to five days in a row.