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Path to higher-quality milk and profits can be found in DNA

Michael Gallenberger Published on 31 October 2011

Mastitis causes more than $2 billion in production losses to the U.S. dairy industry each year. Traditional mastitis testing can be prone to error and be slow – barriers that may prevent dairy farmers from testing as often as necessary. Bacterial culturing has been the standard method for mastitis testing for many years.

However, this method has several drawbacks which cause it to be an inefficient method in mastitis analysis. Bacterial culturing is slow, inaccurate, prone to errors and, most importantly, it cannot be used with preserved milk samples.

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Dairy herd improvement samples used for somatic cell counts cannot be utilized in mastitis testing where bacterial culturing is the method of choice.

With consumers having much more information about their food supply today, milk quality has become a big issue in terms of both food safety and dairy producer profits. Producers need to be aware of both clinical and subclinical mastitis.

In the case of subclinical mastitis, the stage of the disease symptoms are not obvious but can still be creating high somatic cell counts (SCC), and in today’s market that usually means lower prices for the producer. When subclinical mastitis exists undiscovered, it can also give the invasive bacteria a better chance to establish chronic infections that may be resistant to antibiotic therapies.

Timely information allows producers and their herd veterinarians to develop a plan and act on it before it is too late. Through the addition of new testing methods known as PCR- (polymerase chain reaction) based assays, we have seen an improvement in the timeliness and accuracy of mastitis testing in our lab.

With earlier identification and actionable results, herd downtime can be reduced and milk quality improved. It continues to be important that the dairy testing lab, the dairyman and the herd veterinarian work together to minimize the impact of mastitis on the farm.

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While there is little new about the devastating and rising costs of mastitis on the farm, we’ve added this new, leading-edge PCR test to identify mastitis-causing bacteria. PCR is a molecular biology technique which is used to amplify the bacterial DNA present in a sample (like milk) to a detectable level.

The reason this is big news for dairy producers is because this new test is faster, more convenient and more accurate compared to traditional bacterial culturing for the identification of mastitis-causing bacteria.

The test we use in our laboratory is the Thermo Scientific PathoProof Bovine Mastitis PCR assay. It is based on real-time PCR technology – a technology widely used in hospital and research laboratories and for various diagnostic applications.

It requires no bacterial culturing steps, thus overcoming the problems related to culturing. The testing is not dependent on how bacteria grow – whether they are slower-growing, like Mycoplasma, growth-inhibited or shed in low numbers. One additional benefit of PCR-based testing is that both fresh and preserved milk samples can be used.

Our lab, based in Kewaunee, Wisconsin, is one of the first labs to bring this new technology into the U.S. We began testing with this new technology in late 2010 and, initially, we averaged about 150 PCR tests per month, but since then we have seen months that exceeded 1,000 tests and our numbers continue to grow.

In our lab, we give the producers the option to choose the PCR-based test and then receive a report that gives them the results of the test in a complete, easy-to-read format. We will also send the report to their herd veterinarian, if requested.

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There are several reasons why PCR-based testing is more accurate. First of all, it has high sensitivity even for samples missed in culture testing. What’s more, the test results are objective, meaning they don’t require visual interpretation, which helps prevent errors.

Finally, the automated reader only requires about two to three days training by a company representative, so the lab is up and running these tests quickly.

The PCR-based tests only take about three to four hours to run and then are completed and reported within a 24-hour to 48-hour window. The quickness of getting these test results to the dairy producer allows them to work with their herd veterinarians in order to develop a rapid, targeted and informed treatment approach.

Our dairy farmers have appreciated having these better tools for fighting mastitis, improving milk quality and making money. PD

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Michael Gallenberger
Gallenberger
Dairy Records

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