Originally published: https://www.thermofisher.com/blog/behindthebench/pcr-testing-mastitis-diagnosis-management/

PCR Testing for Mastitis Diagnosis and Management

By Behind The Bench Staff

Dairy Herd Health Information Fast and Easy

CentralStar Cooperative – PCR Is a Game Changer for Mastitis Management

Michele Kaufmann, customer solutions advisor at CentralStar Cooperative, explained the value of PCR testing for mastitis management in a webinar offered by Thermo Fisher Scientific.

Pioneers of Dairy Herd Information Milk Samples

Milk Weight Data

Midwest-based CentralStar Cooperative pioneered testing of dairy herd information (DHI) milk samples for the management of cow herd health and disease in the US. The cooperative provides reliable diagnostic testing services for producers and uses test methods that are easier and more economical than traditional methods like culturing. Milk weight data is collected on farms along with a sample from each cow to test for fat content, protein content, and somatic cell count (SCC).

The information about fat and protein content helps farmers make herd management decisions related to reproduction and nutrition. A high SCC may indicate a cow has an infection like mastitis, which can affect milk quality. However, an SCC does not provide specific information about the organism that is causing the infection. PCR data allow dairy producers to identify the causative agents of mastitis. PCR can be used to monitor and track the occurrence of mastitis on farms, and its sensitivity and specificity make it useful for analyzing bulk milk samples as well as samples from individual cows.

Mastitis Can Devastate Dairy Business

“The impact of mastitis can be staggering to a dairy. This is what caused CentralStar to want to raise the bar for detection and management,” said Kaufmann. “In 2014, we chose mastitis PCR—the ability to detect the DNA of various mastitis-causing pathogens in a preserved DHI sample or in the treated animal. PCR is a game changer for mastitis management compared to traditional methods.”

PCR Provides Additional Herd health Information With No Extra Work

PCR for mastitis provides CentralStar customers additional herd health information with no extra work on their part. Producers and veterinarians simply request the test, and CentralStar handles the rest. CentralStar customers continue to recognize the benefits of PCR as a diagnostic tool. In 2021, the number of milk samples tested for mastitis by PCR increased by 52%. In the first half of the current fiscal year, CentralStar has tested more than 21,000 milk samples for mastitis using PCR.

“This has been the most consistent test in terms of growth in the last year with no indication that it will be slowing down. Dairy producers appreciate the simplicity of the test and that it brings them a wealth of knowledge and insight into the udder health of their herds,” said Kaufmann. CentralStar offers a range of testing options, so customers of PCR testing for mastitis can screen for individual pathogens such as Staphylococcus aureus and Mycoplasma bovis. CentralStar also has testing panels that include contagious and environmental pathogens. PCR can be run on preserved DHI samples or hand-stripped samples collected by owners and placed in bulk tanks.

Utilizing PCR Data to Manage Herd Health

Examples of how CentralStar customers utilize mastitis PCR data to manage their herds:

• A 550-cow dairy in Michigan screens all their new cows for aureus. The dairy identified this pathogen on the farm a few years ago and made it a priority to detect and eliminate it from the herd. The dairy has been very successful in reducing the number of infections to nearly zero.
• A 3,600-cow dairy in Wisconsin uses mastitis PCR data to monitor milk quality. They use a combination of DHI data and mastitis PCR results to identify non-profitable cows and screen for contagious pathogens. Having a monthly picture of mastitis pathogens in the herd has been extremely valuable for maintaining high-quality standards for milk.
• A 200-cow dairy in Michigan struggled with traditional milk culture because they consistently received no-growth results. This left them guessing about the cause of rising SCC in their bulk tank. The dairy turned to PCR for mastitis to screen new cows in the herd. After evaluating the DHI data, they found that new cows had the most room for improvement. With guidance about interpreting mastitis PCR results and implementing management changes, the dairy has been able to reduce the SCC in its bulk tank and keep it at a manageable level for three years. Even when there is an occasional spike, the level of SCC has been quickly course-corrected to bring it back down, often with small adjustments.
• A 1,100-cow dairy in Wisconsin recently expanded by purchasing groups of cows. Under the advisement of their herd veterinarian, they have implemented a new cow screening program that allows them to quickly identify and remove infected cows to prevent the spread of contagious pathogens. The dairy continues to use PCR for mastitis to test newly infected animals and make treatment decisions with their veterinarian to keep mastitis under control.
• A bovine veterinarian in Michigan performs hospital pen bulk-tank screening for his customers. He looks for contagious pathogens, to monitor the health of milking herds. The milk from this group is used to feed calves, so he also tracks environmental pathogens to see how they may impact calf health.

Most Common Causative Agents of Mastitis

Streptococcus dysgalactiae

Kaufmann said they have seen an increase in Streptococcus dysgalactiae cases recently, but that‘s not surprising.

“We know that S. dysgalactiae likes a warm and damp environment and that it thrives in organic matter, so it’s the perfect recipe for springtime weather in Michigan. Luckily, for the most part, it’s an easy pathogen to manage by keeping things clean and dry. However, it has brought on a bit of stress because our producers see the increase in their bulk tank or an increase in mastitis incidences, which frustrates them.”

Adoption of PCR Testing for Mastitis

With PCR test results, CentralStar can identify trends in pathogen prevalence and help customers effectively manage their pathogen loads. According to Kaufmann, adoption of PCR for mastitis testing is an ongoing effort.

“We have some early adopters who were very interested right away, but there’s also going to be plenty of people who are skeptical and want to see the proof. But what we’re seeing, especially in the last few years, is a big shift toward PCR. I think that is partially because people are getting frustrated with a no-growth answer on a culture plate. When you’re looking at whether or not to treat a cow, if there’s no growth, you don’t treat. But it still doesn’t give you an idea of what happened to cause that mastitis issue or how to prevent it from happening again. That’s why some producers and vets are turning to PCR as a way to find the answer. They’re also looking at PCR more as a way to manage the whole herd and considering what they need to do to manage and prevent it rather than just making treatment decisions.”

PCR Benefits for Herd Management

“Mastitis treatments have gotten more difficult – more expensive, it’s hard to get products, and there are fewer products available,” stated Kaufmann. “I think people are starting to see that managing the herd with PCR can be more beneficial and give you more insight than trying to react to a culture result. There’s always some skeptics who think it’s too sensitive or too expensive, but I think more and more people are really jumping on board and seeing that it is a really beneficial tool.”

Samples Collected From Across the US – PCR for Fast Results

CentralStar team members are collecting samples on farms in Michigan, Indiana, Wisconsin, Illinois, Iowa, Minnesota, and Ohio. In addition to this, their laboratories in Michigan and Wisconsin receive samples from across the country. The same 48-hour turnaround time applies to all sample types submitted for PCR for mastitis. Results are emailed directly to producers, so they can make timely decisions regarding mastitis management.

On-Demand Webinar – Watch Now

» CentralStar Cooperative  – Mastitis Testing With PCR

Related: Diagnosing Bovine Mastitis: Real-Time PCR for Fast Results