Measuring Success

How do you measure success regarding milk quality? Check out these key  performance indicators for qualitative bulk milk cultures to see how your farm is performing.

Key performance indicator (KPI), sources and suggested interpretation of bulk tank milk culture results. a   


Streptococcus agalactiae




Staphylococcus aureus



Mycoplasma spp.





Coagulase-negative Staphylococci (CNS)


Environmental streptococci




















<250 – 500














Typical Sources in Milk

Mastitis infections




Mastitis infections, teat skin


Mastitis infections





Teat skin contaminants



Contamination from dirty udders or milking equipment; occasionally caused by mastitis infections


Pseudomonas spp.




Bacillus spp.

Isolation of any colonies indicates likely presence of infected cows

For both pathogens, isolation from bulk tank milk indicates the likely presence of infected cows; repeated isolation in BTM usually found in herds with greater prevalence

Investigate pre-milking teat disinfection

When env. strep and coliforms both exceed goals it is a strong indication that the source was poor milking hygiene.

Presence of significant numbers often indicates contamination of milk with water
Presence of significant numbers often indicates poor milk sample handling

aadapted from Farnsworth, 1993 and Jayarao et al., 2004
Farnsworth RJ. 1993. Microbiologic examination of bulk tank milk. Vet Clinics North America, Food Anim. Pract, 9:469-474.
Jayarao, B.M., S.R. Pillai, A.A. Sawant, D.R. Wolfgang and N.V. Hegde. 2004. Guidelines for monitoring bulk tank milk somatic cell and bacterial counts. J. Dairy Sci. 87:3561-3573.

Other key performance indicators include:
• Microbial quality bulk milk
• Milking systems & performance
• Subclinical mastitis

UW-Milk Quality promotes an integrated, team-based approach to best manage udder health and milk quality.  Producing high quality milk is not a one-person job.  It takes farmers and their local dairy advisors to be able to evaluate, manage and improve milk quality.  At UW-Milk Quality, we develop tools and resources to help dairy producers meet their milk quality goals and increase farm profitability.

For more information regarding milk quality, please visit UW-Milk Quality or contact UW-Extension Milk Quality Specialist Pam Ruegg.  For more information regarding milking systems, please visit UW Milking Research and Instruction Laboratory or contact UW-Extension Milking Systems Specialist Doug Reinemann.

From: Ruegg, P.L. 2011. Managing Mastitis and Producing High Quality Milk. Chapter 18 in Dairy Cattle Production Medicine. C. Risco and P. Melendez, (editors), Wiley-Blackwell Publishing, LTD.
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