It is important to test bulk tank samples for mycoplasma mastitis on a regular basis because cows infected with Mycoplasma often are intermittent shedders and a single bulk-tank sample might miss the shedders.
Roger Winter, a technical services veterinarian for AgriLabs, suggests taking bulk-tank samples from particular strings or groups of cows rather than the entire herd, if at all possible. That way, the dilution factor won’t be as great.
The frequency of cow sampling will depend on the incidence of clinical signs and risk factors in the dairy. It could be as frequent as daily or weekly, but certainly monthly at a minimum.