Mastitis is a costly disease both for farmers and the dairy industry as a whole with veterinary costs, antibiotics, milk retentions, and other unwanted costs. Somatic cells are white blood cells and cells from the udder secretory tissue with purpose of eliminating infections. In an uninfected gland, the somatic cell count is low however with an infection, the body sends high numbers of somatic cells to fight off the disease. Hence it is a common measure to use somatic cell count to measue gland health and milk quality. Mastitis can be clinical (SCC usually > 1 mill.) or sub-clinical (usually 200,000 < SCC < 1 mill.).

We have been able to spot cows with mastitis for many years using somatic cell count as an indicator, for example, with the FOSS Fossomatic analyser.  So, why are scientists and researchers still talking about the problem of mastitis?

Pathogens that cause mastitis are constantly evolving and this requires altered mastitis management programs. Apart from that dairy cows have evolved to produce evidently more milk today. The ongoing challenge for researchers is to keep track and adjust accordingly to these alterations.

Can you give an idea of the scope of the problem with mastitis today – how much milk are we losing to the disease?

Especially with today’s high yielding dairy cows, the energy demand often exceeds the energy in take leading to stress on the metabolic system making them more vulnerabile to diseases and disorders. 50 clinical and subclinical cases of mastitis occur per 100 cows each year and cases occurring in the early stages of lactation can cause reduced production accumulating up to 500kg of milk.

When cows receive mastitis treatment (i.e. antibiotics), their milk cannot enter the food chain and the amount of discarded milk can easily be 100-300 kg. Considering all costs related to mastitis (for example, treatment, discarded milk, increased labour), one case costs the dairy farmer from around €100 to €950.

Why aren’t raw milk testing laboratories doing more to combat mastitis through dairy herd improvement (DHI) programs?

Tests for determination of mastitis causing pathogens using the regular DHI samples are currently being introduced in many countries around the globe. FOSS is constantly in dialogue with raw milk testing laboratories to discuss new solutions that can eventually help the dairy farmers to improve their management

What methods are available to laboratories to provide more and better analysis data?

Up to 16 different mastitis-causing pathogens can be analyzed using a PCR (polymerase chain reaction) test. While the PCR test can be done within five hours, the interpretation of test results can be difficult, for example, due to false-positive results because of contamination or carry-over. The test is also quite pricy for the dairy farmer (roughly €15-€20 per cow).

Another alternative is using lactoferrin, a glycoprotein, as a parameter. It can be predicted using high-throughput Fourier transform infrared technology instruments such as the FOSS Milkoscan, which would allow an analysis at low cost, or using a costlier and labor intensive enzyme-linked immunosorbent assay (ELISA) test. However this method is still considered controversial scientific literature with studies indicating that changes in concentration of lactoferrin can only be seen for the case of clinical mastitis.

Thirdly, milk amyloid A (MAA), a (lipo-) protein with various functions in the immune system, has been identified as an indicator for mastitis. It can only be determined by purpose-built ELISA, which is labour and cost intensive and requires the DHI samples to be pulled out of the routine work flow in a laboratory. Beyond that, the value of testing MAA has only been seen when quarter-foremilk samples were used which gives extra work for dairy farmers.

In summary, the well-established somatic cell count (SCC) is still the ultimate parameter available for mastitis screening. However, the need for an additional biomarker, that would allow a more refined mastitis screening (e.g., detection of the onset of the disease) and can be measured at low cost on DHI samples, remains

What will it take to reduce the impact of mastitis – what is it that dairy farmers need? 

Today, mastitis management is often based on reacting to elevated somatic cell counts in DHI samples, often with antibiotic treatment preventive measures and, here, biomarkers that could indicate the onset of mastitis and probability of cure would be of extraordinary value for the dairy industry.

What impact would it have on global milk production if we can reduce the incidence of mastitis from current levels by, say, 10%? 

It would definitely be more efficient use of precious resources such as feed and water. The administration of antibiotics used for mastitis treatment could be reduced. Furthermore the global threat of antimicrobial resistance in human beings while any way to help improve productivity can only be a good thing for dairy farmers struggling with milk price volatility.

So what’s the solution?

Besides looking at the total somatic cell count introduced by FOSS in the 80s, a differentiation of the somatic cells into individual cell populations can yield very valuable information as it allows a more detailed evaluation of the actual udder health status of cows compared to using SCC alone.

What is cell differentiation – how does the principle work?

Cell differentiation refers to the differentiation of immune cells occurring in milk into lymphocytes, macrophages, and polymorphonuclear neutrophils. three cell populations play a vital role in inflammatory responses within the mammary gland distribution of leukocytes differs between normal milk and mastitic milk. Specifically, proportions of PMN can reach up to 95% in milk from cows with mastitis.

Summing up, the characteristics of somatic cells together with the overall count could provide new levels of information for a more effective management of the disease.

When do you think the agri industry will have the power to reduce mastitis? 

In my view, the next few years will see big advances, but this will involve action from many stakeholders. Our vision is to provide analytical solutions that provide increasingly sophisticated levels of information. In the next step, the data needs to be converted to meaningful information so that the dairy farmer can make sound decisions in terms of dairy herd management.

Communication of the information to the dairy farmer is a crucial aspect in this context. Given the complexity of the disease, cross-functional and cross industry collaboration, for example, between DHI organizations, universities and veterinarians will be needed to improve current mastitis management program.

Original Article : https://www.fossanalytics.com/en/news-articles/rmt/mastitis-detection-in-dairy-herds