At PDPW’s Annual Business Conference, Dr. Pam Ruegg spoke on the present challenges against mastitis pathogens, which are vastly different from those 25 years ago. Increasing pathogen diversity changes the criteria for treatments and control programs.
Ruegg conducted a study to identify the mastitis pathogens present in Wisconsin using samples from 51 dairies. Participating farms were required to forestrip during milking as forestripping identifies 50% of mastitis infections.
The most common pathogens found, in order, were:
- No-growth – bacteria not present when the case was found and sampled. This means the cow’s immune response successfully killed the pathogens, or cured the infection.
- E.coli – Environmental bacteria, cow’s immune system usually successfully kills, thereby eliminating the need for treatment.
- Environmental strep – Requires antibiotic treatment to effectively prevent spread of subclinical cases.
- Klebsiella

25% of mastitis cases were no-growth, and therefore non-treatable. 17% of cases were bacteria that don’t respond to antimicrobial therapy. That’s 42% of mastitis cases that don’t need antibiotic treatments. This poses the question, are we over treating cows on our farms?
In order to avoid unnecessary use of antibiotics, we need to identify what pathogen is causing the infection. Aside from ethical issues of overusing antibiotics, there is also the cost issue — keeping in mind that over 80% of antibiotics used on dairies are for control and treatment of mastitis.
Testing is the only way to determine whether or not that cow in your parlor exhibiting mastitis symptoms has a pathogen meriting the cost of an antibiotic treatment. Fortunately we have many testing options, including on-farm culturing. Vet clinics and reference labs also handle milk culturing.
Proper Sampling Technique for culture or other tests:
- Wear gloves
- Use a sterile container
- Pre-dip, dry teat, (make sure you forestrip)use alcohol scrub with 2 hands and THOROUGHLY clean teat end
- Take sample without cross contamination
- Immediately cool or freeze
If performing on-farm culturing, start as soon as possible. If sending to a lab, cool immediately to prevent incubation of other bacteria.
Testing milk samples to identify pathogens needing antibiotic treatments can typically reduce mastitis treatment costs 40%. How much would a 40% reduction in your treatment costs look like?