Module 12: Intro to Mastitis Testing

Module 12.5: Evaluating mastitis at the herd level

Bulk Tank Culture

Bulk tank culture is an important part of the mastitis control program to determine if there are any contagious pathogens at the herd level.

In the milking parlor, the milk from all cows is commingled into a single tank (bulk tank). When screening for contagious pathogens, milk is collected from the bulk tank for 3 to 5 consecutive days, and submitted for culture.

Process of Bulk Tank Culture
Bulk Tank Culture

What are the contagious pathogens we are trying to detect?

  • Staph aureus
  • Strep ag
  • Mycoplasma
  • Prototheca

If these contagious pathogens are present in bulk milk, it means there are likely cows infected with those pathogens in the herd.

The bulk tank culture is also used to monitor milking time hygiene by tracking the level of environmental bacteria (Environmental Streps, Coliforms) in the milk. The presence of those organisms in bulk milk is primarily due to contamination during milking, NOT from cows infected with those organisms.


Key Takeaways

  • Mastitis is a common problem in diary herds worldwide and can lead to tremendous economic losses
  • The California mastitis test (CMT) is a screening tool to identify subclinical mastitis, specifically elevated somatic cell counts
  • Bulk tank cultures screen for environmental and contagious pathogens at the herd level
  • Individual milk cultures are used on an individual cow with clinical mastitis to characterize the specific environmental or contagious pathogen(s) that are causing disease
You have now reached the end of Module 12. If you are enrolled in CVM 6925, please go to the Canvas page and take the quiz: “Module 12: Mastitis quiz.” There is an assignment that accompanies the in-person laboratory for this module.

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