Interpretation of MQC-C data
Mastitis is one of the most common health problems in dairy farming and effects milk quality, milk quantity and animal welfare.
Somatic cell count (SCC) is a parameter that is often used for (sub)clinical mastitis diagnosis and therefore this parameter is used to improve udder health. A rapid increase in SCC in milk signals inflammation of the udder. Cell counting is therefore relevant in monitoring animal health and triggering proper farm management decisions. SCC insights can either be received by a laboratory or by the MQC-C.
The MQC-C is an additional module for the Astronaut. The device takes a milk sample and adds a reagent liquid to this milk sample. Based on the viscosity of this sample, a cell count indication will be generated. This test is based on the same principle of a California Mastitis Test. In this test milk samples are collected and after adding reagent the mixture can turn slimy. The more (inflammatory) cells are present in the milk, the slimier the mixture becomes.
MQC-C versus laboratory cell count determination
Laboratory cell count measurements are a diagnostic test. With this test the presence or absence of a disease can be established.
Laboratory tests are usually performed every three to six weeks. The samples used for the lab cell count measurements consist of a representative sample of the whole milking. At the lab, a (automatic) microscopic count takes place. By staining the DNA of somatic cells, a fluorescent microscope can be used to count the glowing cells and determine the SCC. The tests are done in a controlled environment with steady temperature, humidity and clean air by a diagnostic tool which gives an accurate and precise outcome.
The MQC-C test is a screening tool; therefore, it indicates a suspicion of a disease. The purpose of the test is a screening and is accurate but not precise. The outcome of the test can be used to find abnormalities with an individual cow. As with any screening test, errors will occur when solely depending on a single test. To minimize the amount of error, screening tests are taken on a regular basis. Therefore, the MQC-C performs a test every three milkings (with smart-sampling). However, when the test results in a high SCC (>250.000 cells/mL), the MQC-C takes a sample of every milking.
More frequent measurements, such as with the MQC-C, possibly result in earlier diagnosis. The MQC-C is developed to find cows that require attention on udder health. With every measurement, the MQC-C performs an online California Mastitis Test. During this test, the Astronaut takes a sample of 11 mL after the first pump stroke. This sample is mixed with a reagent liquid, subsequently the viscosity of the mixture is measured. The measured viscosity is transformed into a digital value, expressed in cells/mL. The thicker the solution, the higher the cell count. Research shows that the correlation between laboratory and MQC-C measurements is less precise in the low cell count ranges (<200.000 cells/mL), while higher cell count ranges (> 500,000 cells/mL) show a fair to good correlation. The value shown in Horizon is a geometric average of the last three measurements.
In summary: The MQC-C test is not designed to be comparable to laboratory SCC in terms of test characteristics and accuracy. The true value is in the fact it gives more frequent measurements and therefore insights for a farmer to act upon.
Fast detection of (sub)clinical mastitis
Close monitoring of individual cow udder health is essential for identification of cows in the early stages of an intramammary infection, as well as timely initiation of treatment and assessment of recovery. With an automatic milking system, a farmer can rely on in- or online sensor systems for identification of cows with milk not meeting quality standards (e.g., milk of cows with an intramammary infection).
Research revealed that the performance of a mastitis detection system improves when SCC information was added to a detection model using conductivity information. Lely Horizon (health tasks 10, 12 and 23) combines the information from all milk sensors on the Astronaut (milk yield, conductivity, color, and optional MQC-C), therefore cows in the early stages of an intramammary infection, can be detected timely and notified towards the farmer which gives the opportunity for a better recovery.
Cows with chronic (subclinical) mastitis often fluctuate in cell count. Daily measurement of cell counts helps to identifies cows with this condition. It appears that these cows do not always get noticed during laboratory tests, because of the fluctuations in their cell count. They can be detected by the MQC-C since these measurements are daily and therefore display fluctuations in cell count patterns.
Selective Dry Cow Therapy
The dry period is an important resting period for the dairy cow, where fresh udder tissue is formed in readiness for the lactation, and it provides an important opportunity to rid the udder of many potential pathogens that can cause mastitis.
A way to prevent mastitis in early lactation is to apply dry cow therapy through administering antibiotics. Giving a long-acting intramammary infusion at the end of lactation has two functions. Firstly, to eliminate current infections on the moment of drying-off and, secondly, to prevent new infections in the dry-period and early lactation. Until a couple of years ago, most cows were dried off using antibiotics. However, antibiotic use creates selective pressure on bacterial populations and contributes to the development of antimicrobial resistance.
There are insights that the three to six weekly laboratory tests do not provide the most accurate information for deciding whether to apply antibiotics for dry cow therapy (selective dry cow therapy). First, because of the time delay between SCC measurement during milk recordings and the actual moment of drying off. It is known that SCC increases at the end of the lactation. This increase is probably caused by a lower milk production, resulting in a higher concentration of somatic cells. In addition, cow health could change significantly just before dry-off, affecting the decision for the right treatment.
The MQC-C enables the construction of individual cow SCC profiles taking (natural) daily variations into account. Deviating patterns in the SCC profile enable an earlier and better-supported diagnosis of mastitis episodes. Frequent measurements and the availability of udder health profiles, including all relevant udder health parameters (such as included in the health reports), support a transition towards effective selective dry cow therapy. It differs per country whether the MQC-C complies with the applicable laws and regulations for selective dry cow therapy.
In conclusion
Overall, the MQC-C is the perfect tool for screening udder health to provide actionable insight for the farmer. It depends on the country whether this method complies with the applicable laws and regulations for selective dry-off therapy. Laboratory tests are more precise than MQC-C measurements. However, the MQC-C is a great tool for udder health management on cow level since this tool provides a profile per cow based on more frequent measurements compared to laboratory tests.