Sarah Wagner learned firsthand that on-farm culturing is not for everyone. Wagner, veterinarian and assistant professor in the Department of Animal Sciences at North Dakota State University, looked at on-farm culturing on four different dairies in South Dakota and Michigan. “There was huge variability between the dairies — some were successful and others were not,” she says.

The difference between success and failure was the person doing the culturing. “The farms with excellent results had an employee who was very motivated and interested in doing the culturing, was trained, followed procedure and had time allotted for culturing,” Wagner says.

On-farm culturing in some instances has been shown to reduce antibiotic usage by 20 percent to 80 percent. It also can help lower somatic cell counts, thereby improving milk quality and production. All of these things increase your profit margin. But, you have to do it right to get the benefit.

People are the key to success

The No. 1 factor that can make or break an on-farm culturing program is the person responsible for the task.

“This is the area where many failures and successes have occurred,” says Keith Sterner, a veterinarian from Iona, Mich.

On-farm culturing can be an exercise in futility if the person responsible for the task does not have proper training and an interest in on-farm microbiology.

“It is very important for cultures to be plated properly. If the person is not plating samples properly, you will have contamination and that can lead to misdiagnosis,” Wagner explains. If they aren’t trained properly to read plates and recognize contaminated samples, you will be spending money to get bad information. 

“We started on-farm culturing on one of our dairies, about 5-years ago, and it became evident that it wasn’t ready for culturing,” says Michael Pedreiro, vice president and chief operating officer for Dairy Production Systems in High Springs, Fla. “Procedures weren’t followed properly, and we were getting contamination of our samples, which led to a higher incidence of growth on both sides of the plate — it was a disaster.” The dairy has since implemented regularly scheduled re-training courses to ensure it stays in compliance with plating procedures.

“On another dairy we operate, we have been able to reduce our antibiotic usage by 35 percent and lowered our SCC from 280,000 to 120,000. This was due to several factors, but one of the biggest reasons was our on-farm culturing program,” says Pedreiro. “The difference was this dairy was ready to take on the task and the technician’s level of interest.”

“Culturing is not something that can be tacked onto someone’s job,” Wagner adds. “The individual in charge of culturing needs to be able to set at least one hour per day aside to perform these tasks.” And, with one person in charge of reading the cultures, you reduce the problem of results being interpreted differently.

It pays to do it right

If on-farm culturing is done well, it will pay for itself in the money you save by not treating cows that do not require treatment.

A tube of mastitis treatment costs anywhere from $1.50 to $3. And, some tubes require once-a-day therapy, others twice-a-day therapy. Depending upon the treatment and length of treatment, the cost for mastitis tubes can range from $9 to $24.

Milk discard is generally the most expensive part of mastitis therapy. At $18 per hundredweight, five days of milk discarded at 50 pounds per day equals $45. This treatment and discard rate will cost you anywhere from $54 to $69 per mastitis case. If you add in labor, you are looking at $125 or more per case. Compare that to the $4 you spend to culture a milk sample on-farm. 

Twenty-five to 30 percent of cultured samples will have no growth. Many no growths are indicative of a gram-negative infection which has a high self-cure rate, so treatment may not be necessary and you save on antibiotics. 

The economic advantage goes to culturing, but it must be done right.

Selecting cows to culture

target three main groups with an on-farm culturing program, says Mark van der List, veterinarian and dairy technical managing consultant for Fort Dodge Animal Health, including:

  • Cows and heifers coming fresh.
  • Cows with clinical mastitis.
  • Cows with a high somatic cell count at DHIA test.

Research shows that 62 percent of cows freshen with subclinical mastitis. “On-farm culturing allows you to target your antibiotic therapy,” says van der List.

Disposing of culture plates 

It is very important to dispose of culture plates in such a manner that you don’t reintroduce pathogens back into the environment. “Culture plates are biohazard material and must be disposed of properly,” explains Kathy Glenn, microbiologist at the Veterinary Medicine Teaching Research Center in Tulare, Calif. She reminds producers that bleach has to come in contact with culture plates for 20 minutes in order to kill bacteria. “If you aren’t disposing of your plates properly, this could lead to a potential disease outbreak on your farm,” she adds.

It is, but only if you do it right.  

Enact quality control

to ensure that you are reading and interpreting cultures correctly, periodically plate milk samples twice. Send one set to a lab and culture the other one on-farm. “This way, you can correlate your readings with the lab, making sure you are seeing the same types of growth patterns (and) giving yourself a measure of quality control,” says Sarah Wagner, assistant professor in the Department of Animal Sciences at North Dakota State University. Milk samples can also be frozen; if a cow does not respond to treatment, the frozen sample can be submitted to a lab to double-check it.

In addition to quality control, work with your veterinarian to interpret culture results and set up treatment protocols, says Gary Neubauer, veterinarian with Pfizer Animal Health. Information gained from culturing is valuable for its timeliness in identifying and treating mastitis, as well as developing control strategies.

Case study: Rich-Ro Farms, St. Johns, Mich.


Rich-Ro farms implemented an on-farm culturing program for its 1,700-cow herd in February 2008. “On-farm culturing was something I was interested in learning,” says Rena Brodbeck, herd manager at Rich-Ro Farms.

Time and training was involved in getting started. “We worked with our veterinarian to develop the program, set treatment protocols and learn how to sample, culture, plate and read results,” she says.

Each Tuesday, the veterinarian stops by to double-check the farm’s work.

On-farm culturing has made a significant difference. Somatic cell counts have dropped from 280,000 to 152,000, qualifying the farm for milk-quality premiums. Antibiotic usage has been cut by 35 percent.


More information on the Web

To learn more about on-farm culturing supplies and how to culture, go to: