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Culturing on-farm can help control mastitis costs

Kelli Boylen for Progressive Dairy Published on 09 June 2020

On-farm culturing is a useful tool for mastitis management. It allows for faster response to infections, saves money and helps to identify causes to help with prevention, according to Dr. Ginger Fenton, dairy extension educator at Penn State University.

On-farm culturing can be especially useful when used in conjunction with other management and information, she says. It can also help with controlling the costs of mastitis by reducing treatment costs and dumping milk and increase overall herd health because of reducing disease susceptibility risks.



When implementing an on-farm culturing program, there can be a bit of a learning curve, she says; changes may be gradual. She encourages producers to culture treated cows again 10-14 days later.

Fenton recommends a quad-plate culturing system, which has four separate agars (mediums for growing bacteria) on one plate.

In addition to a quality incubator for growing cultures, she recommends having gloves, swabs, quad-plates, tubes, markers, alcohol wipes and household bleach. A refrigerator is recommended for storing samples for up to 24 hours before testing; freeze samples that will not be tested within 24 hours.

Sample tubes should be labeled immediately after being gathered with the cow ID, quarter and date, and then also label the bottom of the sample plate (not the lid as they are easily mixed up).

Once testing is done, all plates should be flooded with bleach, sealed or double sealed in a zip-type bag and disposed of where children and animals cannot get into themn. Or, if you have access to an autoclave, use that to safely dispose of the plates.


Always wear gloves when handling samples and testing material. Testing areas should be signed with biohazard warnings. Never eat or drink in testing areas and keep children and animals away. “You are growing pathogens which can cause disease, and you need to use extreme caution,” Fenton says.

When choosing someone to do the testing on your operation, look for someone who is science-minded, pays attention to detail and will follow safety guidelines.

Fenton says it can be frustrating to learn how to read the bacteria growth on the plates, but it will get easier with experience. She notes that if you see more than one type of bacteria growth on a plate, it is likely the sample was contaminated and will have to be redone.

When gathering samples, employees should prep the cow as usual, with extra attention paid to the cleanliness of the teats. The teats farthest from the employee should be swabbed with alcohol, stripped and collected, and then the closer teats should be swabbed with alcohol, stripped and collected. This will help prevent contamination of the closer teats when the employee is reaching across.

She recommends starting with Dairy Herd Information Association (DHIA) records to find cows with high somatic cell counts (SCC) to test, in addition to using the California Mastitis Test (CMT) to screen for issues. Also, ask employees which cows they have concerns about, and have a system for them to alert managers of issues they find, either through a log sheet or white board.

“On-farm culturing screens for possible pathogens and is not diagnostic, and confirmation should be verified by a laboratory. Also, these types of tests are qualitative and not quantitative, so they indicate if a pathogen is present, but not in what amount,” Fenton says.


Just as important as taking good samples and culturing properly, she says detailed records need to be kept of the results of the testing and if the treatments were effective. You need to know what treatments were successful in order to make effective protocols to help solve issues long term. This needs to include considering at what stage of lactation cows are most likely to get mastitis, if not having a closed herd is part of the issue, if the condition of milking equipment is part of the problem or, perhaps, if certain employees are not following protocol.

Simply knowing what types of infections you are dealing with can help with solving the problem long term, Fenton explains.

For example, contagious pathogens, such as Staphylococcus aureus, Streptococcus agalactiae and mycoplasma species reside on udders and teats, can be transferred cow to cow by hands or on equipment, may have spikes in numbers and there may be chronic infections that will need to be culled. Prevention for contagious mastitis may include improved milking protocols, post-dips, treating cows when drying off, maintaining milking equipment and keeping a closed herd.

Environmental pathogens such as Escherichia coli, klebsiella species, Streptococcus uberis and enterobacter species are spread by soil, bedding, manure and water. They usually have a shorter duration and a high clinical infection rate. Bedding management and focusing on udder prep (including pre-dip and pre-stripping) can help resolve issues.

“Culturing is not considered an endpoint and will not dictate a need for treatment in every case. Using clues to determine the cause of mastitis can allow for a faster response on the part of the producer, as preliminary results from this process can be obtained within 24 hours, and final results within 48 hours. This can save time and money, as well as allowing for a more judicious use of antibiotics, since not all cases will require treatment.”

Managers need to observe employees to make sure protocols are being followed and communicated well. Just saying they need to “dip, strip, dry and apply” is not enough for someone from outside the dairy industry to come in and know exactly what that means, she says. “If you want people to perform things, they have to understand the ‘why.’”

Communicate in a language the employees understand, be it with a translator, photos or diagrams. Explain exactly what you want them to do, which products for what durations and be sure to include the reasons for doing it that way.

All employees should also be trained to know the visual signs of mastitis and how to alert others of their concerns about the cow’s wellness.

While working on a plan for on-farm culturing, deciding treatment protocols and standard operating procedures for employees, Fenton recommends always working with your veterinarian and/or local dairy extension.  end mark

Ginger Fenton deals with a variety of dairy topics, but food safety, both on-farm and at processing plants, is one of her areas of expertise.

Kelli Boylen is a freelancer based in northeast Iowa.