Mastitis bacteriology and sampling

By collecting samples of the milk produced by cows suffering from the symptoms of mastitis, and indeed samples of cows identified as having high Somatic Cell Counts, it enables us to identify:

  • Which pathogen or pathogens are to blame, in order to target effective treatment, and;
  • Which control measures can be implemented on the farm to reduce the incidence of the disease.

Using a California milk test

By identifying the causal agent, the best antibiotic can be used to counter a specific bacterium species; the bacteriology process in the laboratory produces cultures of the pathogen isolated from the sample and various chemicals are used to stain the bacteria in order to identify them, as different species behave in different ways when stained.

Other identifying methods are used, such as the shape and size of the bacteria when looked at under the microscope. In most circumstances, samples are sent to a laboratory for analysis.

In some cases, an inconsistent result is achieved, particularly when several species are present and cannot be adequately isolated, where antibiotic residues have affected bacterial growth on the culture plate or where, by the time the symptoms were noted and the sample taken, the cow's immune response may already have successfully controlled the infection.

Aseptic milk sample collection

It is imperative for any sample to be collected as hygienically as possible to avoid any contamination; Sample tubes should be labelled, clean disposable gloves should be worn and kept clean, and clean towels must be used for wiping and drying. Before sampling:

  • Teats should be washed and must be thoroughly dried.
  • Teats should be dipped in an effective germicidal teat pre-dip and the appropriate contact time allowed before wiping off.
  • The teats should be swabbed with surgical spirit, starting with the furthest away and working towards the closest teat, then allowed to dry.
  • The first four to six squirts of milk should be discarded, and then the teats swabbed with surgical spirit a second time and allowed to dry.

The sample tube should be held at an angle under the teats so that material cannot fall into the opening; the lid should be opened with the thumb and forefinger and held as a shield to prevent any contaminants from falling into the tube. Nothing should be allowed to come in contact with the mouth of the tube:

  • Two or three squirts of milk from each quarter should be collected, starting with the closest quarters and working toward the ones farthest away.
  • The container should be closed before removing it from beneath the teats.
  • Samples should be refrigerated ideally until they reach the lab. If samples will not reach the lab within 24 hours, they should be frozen and kept frozen until they reach the lab.

Related links and publications



Our tools and resources to help you manage mastitis on your farm

Watch our short video about how to perform a california milk test