Milk Culture & Sensitivity Testing

Individual milk samples from cows with mastitis or bulk tank samples from herds with high somatic cell counts (SCC) can be cultured to identify the bacteria present in the sample. Identification of the bacteria causing mastitis or elevated SCCs is critical to control the disease as some bacteria may originate from the environment while others originate from other cows in the herd and require different control measures.
Antibiotic sensitivity testing is carried out on bacteria isolated from milk samples to identify those antibiotics suitable for treatment of mastitis or for dry-cow therapy.
The most important element of milk culture and sensitivity testing is the collection of the milk sample on the farm. Contamination of the sample from the environment, from dirty teats or from the sampler’s hands can occur quite easily. Where 3 or more bacterial species are identified in a milk sample from a cow with mastitis, the result is likely to represent sample contamination rather than infection.

For further information please contact the laboratory at:

  • Correct sampling technique is essential when trying to identify mastitis causing bacteria. Contamination can occur through the hands of the sampler, cows teat not cleaned or dried before sample is taken, and the housing environment.
  • Collect milk samples before antibiotics are administered.
  • Sterile containers with NO preservative must be used.
  • Gloves must be worn. Do not take milk samples using milking equipment.
  • Samples are best taken prior to milking.
Procedure for taking individual milk samples:
  • Label sample container prior to use (i.e. date, farmer, cow, quarter RF, RH, LF, LH).
  • Clean the teats by brushing off any heavy dirt material first, then washing and drying the teats.
  • Scrub each teat with 70% alcohol (an alcohol wipe can be used, change for each teat).
  • Discard the first stream of milk obtained from the quarter, hold the sample container at a 45 degree angle and do not allow the teat to touch the container. (1-3 streams of milk is sufficient).
  • If taking a composite sample (4 teats), collect an equal volume from each teat (1-2 streams of milk per teat is sufficient).
  • Fridge samples immediately (or put on ice) and deliver to the lab within 24 hrs.
Procedure for taking bulk milk samples:
  • Agitate the bulk milk tank for a minimum of 5 minutes.
  • Use a sterile dipper to collect the sample at the top of the tank (never from the bottom).
  • Fridge sample immediately (or put on ice) and deliver to the lab within 24 hrs.