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Stop waiting for ‘The Call’: On-farm culturing can be effective

Linda Tikofsky Published on 13 May 2011

At the first sign of a new case of mastitis, the last thing the herdsman wants is to be left waiting for a call from the milk quality lab to tell them if treatment is worth the expense. You’ve been taught that prompt attention to the health status of your cows always pays off.

Meanwhile, the case of mastitis is getting worse and you’re not sure what treatment route to follow. The call, e-mail or mailed letter you’re waiting for will tell you the results of the mastitic milk sample you sent over a week ago.



So, do you treat or do you wait? Or is there a more serious issue on your hands?

A growing number of farms whose local veterinarians do not offer milk culturing services are bringing microbiology to the milk house. On-farm milk culturing (OFMC) can be an effective option for a farm seeking to make treatment decisions sooner, save money and determine what mastitis-causing pathogens are being dealt with – especially when convenient local options are not available.

Don’t be mistaken, on-farm culturing is not for everyone. A study completed in the early 2000s revealed that of 81 Midwest farms who had begun on-farm culturing within the previous 2.5 years, 26 of the farms (32 percent) had discontinued it.

In order for it to be most useful, a farm should have enough cows with mastitis problems in their herd to make the training and equipment costs worthwhile. In addition, culturing must be approached scientifically in a clean, careful environment. Each farm should designate the culturing responsibility to one member of the farm’s staff who is given time in their workday to complete necessary lab work.

Getting started
At the most basic level, OFMC will allow you to determine if the pathogens causing mastitis are gram-positive or gram-negative. In other words, should I use an intramammary antibiotic treatment or can I opt to allow the cow to attempt to eliminate the infection herself?


If you believe that OFMC may be right for you, several commercially offered systems are available. A local veterinarian or extension employee could be a great resource for finding the proper equipment. Culture plates containing growth media or agar are an essential tool.

For beginners, a bi-plate is a simple place to start. These plates contain a divider with two different types of growth medium on either side.

Each section of the plate is then swabbed with the milk sample that has been collected appropriately. After 24 hours of incubation, you can identify if the mastitis is gram-negative or gram-positive based upon the bacterial growth pattern.

It is important to remember, though, when no growth occurs there could be other organisms present, such as mycoplasma – a much more serious mastitis issue. Therefore, OFMC should never fully replace a high-quality off-farm laboratory.

Targeted treatment
Training manuals are available to assist you in reading the results of cultures. However, hands-on training may be a simpler way to learn. Contact local extension personnel, a local milk quality lab or your farm’s veterinarian to see if they are available to provide some training.

In the case of gram-positive growth, treatment using intramammary antibiotics (mastitis tubes) will provide the most effective, quickest therapy. Infections caused by gram-negative pathogens, on the other hand, have a high rate of spontaneous cure and most antibiotics have limited efficacy against these pathogens.


For clinical cases of mastitis, making an educated treatment decision 24 hours after detection can make a difference in cow health, treatment costs and milk discarded.

If the specific type of mastitis-causing organism has been identified, it can be a useful tool in selecting intramammary antibiotics for treatment. Culture outcomes should be shared with your veterinarian to develop treatment protocols for your farm. These outcomes may also be compared to the product label to make the most informed targeted treatment.

With targeted treatment, the goal is a better response to treatment of infections caused by gram-positive pathogens like staphylococci (staph) and some environmental streps. A recent study looked at the cost-effectiveness of using on-farm culturing to identify and treat only gram-positive infections. The 189 cases, after accounting for all costs, resulted in a net income of about $3,342 per month.

With many cases of mastitis caused by gram-negative pathogens, the cow will clear the infection on her own without antibiotics. Research has shown that 50 to 60 percent of clinical milk samples would earn a “no treatment” decision because they are negative for bacteria or it is a gram-negative pathogen.

At the end of the day, the information provided by on-farm culturing means producers can save money and increase the odds of a full cure on first treatment. Successful treatment the first time will put a cow back in the tank faster, and milk discarded will be minimized. PD

Linda Tikofsky is a professional services veterinarian with Boehringer Ingelheim Vetmedica, Inc. She is based in Ithaca, N.Y.

References omitted due to space but are available upon request to .

Linda Tikofsky
Boehringer Ingelheim